Directed factor graph based fault diagnosis model construction for mode switching satellite power system

Abstract: Satellite power system is a complex, highly interconnected hybrid system that exhibit nonlinear and mode switching behaviors. Directed factor graph is an inference model for fault diagnosis using probabilistic reasoning techniques. A novel approach for constructing the directed factor graph structure based on hybrid bond graph model is proposed. The system components status and their fault symptoms are treated as hypothesis and evidences respectively. The cause-effect relations between hypothesis and evidences are identified and concluded though qualitative equations and causal path analysis on hybrid bond graph model. A power supply module of a satellite power system is provided as case study to show the feasibility and validity of the proposed method.


Target-driven merging of Taxonomies

Abstract: The proliferation of ontologies and taxonomies in many domains increasingly demands the integration of multiple such ontologies. The goal of ontology integration is to merge two or more given ontologies in order to provide a unified view on the input ontologies while maintaining all information coming from them. We propose a new taxonomy merging algorithm that, given as input two taxonomies and an equivalence matching between them, can generate an integrated taxonomy in a fully automatic manner. The approach is target-driven, i.e. we merge a source taxonomy into the target taxonomy and preserve the structure of the target ontology as much as possible. We also discuss how to extend the merge algorithm providing auxiliary information, like additional relationships between source and target concepts, in order to semantically improve the final result. The algorithm was implemented in a working prototype and evaluated using synthetic and real-world scenarios.


Applying centrality measures to impact analysis: A coauthorship network analysis

Abstract: Many studies on coauthorship networks focus on network topology and network statistical mechanics. This article takes a different approach by studying micro-level network properties, with the aim to apply centrality measures to impact analysis. Using coauthorship data from 16 journals in the field of library and information science (LIS) with a time span of twenty years (1988-2007), we construct an evolving coauthorship network and calculate four centrality measures (closeness, betweenness, degree and PageRank) for authors in this network. We find out that the four centrality measures are significantly correlated with citation counts. We also discuss the usability of centrality measures in author ranking, and suggest that centrality measures can be useful indicators for impact analysis.


Discovering author impact: A PageRank perspective

Abstract: This article provides an alternative perspective for measuring author impact by applying PageRank algorithm to a coauthorship network. A weighted PageRank algorithm considering citation and coauthorship network topology is proposed. We test this algorithm under different damping factors by evaluating author impact in the informetrics research community. In addition, we also compare this weighted PageRank with the h-index, citation, and program committee (PC) membership of the International Society for Scientometrics and Informetrics (ISSI) conferences. Findings show that this weighted PageRank algorithm provides reliable results in measuring author impact.


Popular and/or Prestigious? Measures of Scholarly Esteem

Abstract: Citation analysis does not generally take the quality of citations into account: all citations are weighted equally irrespective of source. However, a scholar may be highly cited but not highly regarded: popularity and prestige are not identical measures of esteem. In this study we define popularity as the number of times an author is cited and prestige as the number of times an author is cited by highly cited papers. Information Retrieval (IR) is the test field. We compare the 40 leading researchers in terms of their popularity and prestige over time. Some authors are ranked high on prestige but not on popularity, while others are ranked high on popularity but not on prestige. We also relate measures of popularity and prestige to date of Ph.D. award, number of key publications, organizational affiliation, receipt of prizes/honors, and gender.


PageRank for ranking authors in co-citation networks

Abstract: Google's PageRank has created a new synergy to information retrieval for a better ranking of Web pages. It ranks documents depending on the topology of the graphs and the weights of the nodes. PageRank has significantly advanced the field of information retrieval and keeps Google ahead of competitors in the search engine market. It has been deployed in bibliometrics to evaluate research impact, yet few of these studies focus on the important impact of the damping factor (d) for ranking purposes. This paper studies how varied damping factors in the PageRank algorithm can provide additional insight into the ranking of authors in an author co-citation network. Furthermore, we propose weighted PageRank algorithms. We select 108 most highly cited authors in the information retrieval (IR) area from the 1970s to 2008 to form the author co-citation network. We calculate the ranks of these 108 authors based on PageRank with damping factor ranging from 0.05 to 0.95. In order to test the relationship between these different measures, we compare PageRank and weighted PageRank results with the citation ranking, h-index, and centrality measures. We found that in our author co-citation network, citation rank is highly correlated with PageRank's with different damping factors and also with different PageRank algorithms; citation rank and PageRank are not significantly correlated with centrality measures; and h-index is not significantly correlated with centrality measures.


Distributed and Optimal Reduced Primal-Dual Algorithm for Uplink OFDM Resource Allocation

Abstract: Orthogonal Frequency Division Multiplexing (OFDM) is the key component of many emerging broadband wireless access standards. The resource allocation in OFDM uplink, however, is challenging due to heterogeneity of users' Quality of Service requirements, channel conditions, and individual resource constraints. We formulate the resource allocation problem as a non-strictly convex optimization problem, which typically has multiple global optimal solutions. We then propose a reduced primal-dual algorithm, which is distributed, low in computational complexity, and probably globally convergent to a global optimal solution. The performance of the algorithm is studied through a realistic OFDM simulator. Compared with the previously proposed centralized optimal algorithm, our algorithm not only significantly reduces the message overhead but also requires less iterations to converge.


Upper Tag Ontology (UTO) For Integrating Social Tagging Data

Abstract: Data integration and mediation have become central concerns of information technology over the past few decades. With the advent of the Web and the rapid increases in the amount of data and the number of Web documents and users, researchers have focused on enhancing the interoperability of data through the development of metadata schemes. Other researchers have looked to the wealth of metadata generated by bookmarking sites on the Social Web. While several existing ontologies capitalize on the semantics of metadata created by tagging activities, the Upper Tag Ontology (UTO) emphasizes the structure of tagging activities to facilitate modeling of tagging data and the integration of data from different bookmarking sites as well as the alignment of tagging ontologies. UTO is described and its utility in harvesting, modeling, integrating, searching and analyzing data is demonstrated with metadata harvested from three major social tagging systems (Delicious, Flickr and YouTube).


Weighted citation: An indicator of an article's prestige

Abstract: We propose using the technique of weighted citation to measure an article's prestige. The technique allocates a different weight to each reference by taking into account the impact of citing journals and citation time intervals. Weighted citation captures prestige, whereas citation counts capture popularity. We compare the value variances for popularity and prestige for articles published in the Journal of the American Society for Information Science and Technology from 1998 to 2007, and find that the majority have comparable status.


Tight Bounds for Lp Samplers, Finding Duplicates in Streams, and Related Problems

Abstract: In this paper, we present near-optimal space bounds for Lp-samplers. Given a stream of updates (additions and subtraction) to the coordinates of an underlying vector x \in R^n, a perfect Lp sampler outputs the i-th coordinate with probability |x_i|^p/||x||_p^p. In SODA 2010, Monemizadeh and Woodruff showed polylog space upper bounds for approximate Lp-samplers and demonstrated various applications of them. Very recently, Andoni, Krauthgamer and Onak improved the upper bounds and gave a O(\epsilon^{-p} log^3 n) space \epsilon relative error and constant failure rate Lp-sampler for p \in [1,2]. In this work, we give another such algorithm requiring only O(\epsilon^{-p} log^2 n) space for p \in (1,2). For p \in (0,1), our space bound is O(\epsilon^{-1} log^2 n), while for the $p=1$ case we have an O(log(1/\epsilon)\epsilon^{-1} log^2 n) space algorithm. We also give a O(log^2 n) bits zero relative error L0-sampler, improving the O(log^3 n) bits algorithm due to Frahling, Indyk and Sohler. As an application of our samplers, we give better upper bounds for the problem of finding duplicates in data streams. In case the length of the stream is longer than the alphabet size, L1 sampling gives us an O(log^2 n) space algorithm, thus improving the previous O(log^3 n) bound due to Gopalan and Radhakrishnan. In the second part of our work, we prove an Omega(log^2 n) lower bound for sampling from 0, \pm 1 vectors (in this special case, the parameter p is not relevant for Lp sampling). This matches the space of our sampling algorithms for constant \epsilon > 0. We also prove tight space lower bounds for the finding duplicates and heavy hitters problems. We obtain these lower bounds using reductions from the communication complexity problem augmented indexing.


Nominal Unification Revisited

Abstract: Nominal unification calculates substitutions that make terms involving binders equal modulo alpha-equivalence. Although nominal unification can be seen as equivalent to Miller's higher-order pattern unification, it has properties, such as the use of first-order terms with names (as opposed to alpha-equivalence classes) and that no new names need to be generated during unification, which set it clearly apart from higher-order pattern unification. The purpose of this paper is to simplify a clunky proof from the original paper on nominal unification and to give an overview over some results about nominal unification.


Unification modulo a partial theory of exponentiation

Abstract: Modular exponentiation is a common mathematical operation in modern cryptography. This, along with modular multiplication at the base and exponent levels (to different moduli) plays an important role in a large number of key agreement protocols. In our earlier work, we gave many decidability as well as undecidability results for multiple equational theories, involving various properties of modular exponentiation. Here, we consider a partial subtheory focussing only on exponentiation and multiplication operators. Two main results are proved. The first result is positive, namely, that the unification problem for the above theory (in which no additional property is assumed of the multiplication operators) is decidable. The second result is negative: if we assume that the two multiplication operators belong to two different abelian groups, then the unification problem becomes undecidable.


A Machine Checked Model of Idempotent MGU Axioms For Lists of Equational Constraints

Abstract: We present formalized proofs verifying that the first-order unification algorithm defined over lists of satisfiable constraints generates a most general unifier (MGU), which also happens to be idempotent. All of our proofs have been formalized in the Coq theorem prover. Our proofs show that finite maps produced by the unification algorithm provide a model of the axioms characterizing idempotent MGUs of lists of constraints. The axioms that serve as the basis for our verification are derived from a standard set by extending them to lists of constraints. For us, constraints are equalities between terms in the language of simple types. Substitutions are formally modeled as finite maps using the Coq library Coq.FSets.FMapInterface. Coq's method of functional induction is the main proof technique used in proving many of the axioms.


Towards Correctness of Program Transformations Through Unification and Critical Pair Computation

Abstract: Correctness of program transformations in extended lambda calculi with a contextual semantics is usually based on reasoning about the operational semantics which is a rewrite semantics. A successful approach to proving correctness is the combination of a context lemma with the computation of overlaps between program transformations and the reduction rules, and then of so-called complete sets of diagrams. The method is similar to the computation of critical pairs for the completion of term rewriting systems. We explore cases where the computation of these overlaps can be done in a first order way by variants of critical pair computation that use unification algorithms. As a case study we apply the method to a lambda calculus with recursive let-expressions and describe an effective unification algorithm to determine all overlaps of a set of transformations with all reduction rules. The unification algorithm employs many-sorted terms, the equational theory of left-commutativity modelling multi-sets, context variables of different kinds and a mechanism for compactly representing binding chains in recursive let-expressions.


On the Complexity of the Tiden-Arnborg Algorithm for Unification modulo One-Sided Distributivity

Abstract: We prove that the Tiden and Arnborg algorithm for equational unification modulo one-sided distributivity is not polynomial time bounded as previously thought. A set of counterexamples is developed that demonstrates that the algorithm goes through exponentially many steps.


Recursive Definitions of Monadic Functions

Abstract: Using standard domain-theoretic fixed-points, we present an approach for defining recursive functions that are formulated in monadic style. The method works both in the simple option monad and the state-exception monad of Isabelle/HOL's imperative programming extension, which results in a convenient definition principle for imperative programs, which were previously hard to define. For such monadic functions, the recursion equation can always be derived without preconditions, even if the function is partial. The construction is easy to automate, and convenient induction principles can be derived automatically.


MiniAgda: Integrating Sized and Dependent Types

Abstract: Sized types are a modular and theoretically well-understood tool for checking termination of recursive and productivity of corecursive definitions. The essential idea is to track structural descent and guardedness in the type system to make termination checking robust and suitable for strong abstractions like higher-order functions and polymorphism. To study the application of sized types to proof assistants and programming languages based on dependent type theory, we have implemented a core language, MiniAgda, with explicit handling of sizes. New considerations were necessary to soundly integrate sized types with dependencies and pattern matching, which was made possible by concepts such as inaccessible patterns and parametric function spaces. This paper provides an introduction to MiniAgda by example and informal explanations of the underlying principles.


Rewriting and Well-Definedness within a Proof System

Abstract: Term rewriting has a significant presence in various areas, not least in automated theorem proving where it is used as a proof technique. Many theorem provers employ specialised proof tactics for rewriting. This results in an interleaving between deduction and computation (i.e., rewriting) steps. If the logic of reasoning supports partial functions, it is necessary that rewriting copes with potentially ill-defined terms. In this paper, we provide a basis for integrating rewriting with a deductive proof system that deals with well-definedness. The definitions and theorems presented in this paper are the theoretical foundations for an extensible rewriting-based prover that has been implemented for the set theoretical formalism Event-B.


Beating the Productivity Checker Using Embedded Languages

Abstract: Some total languages, like Agda and Coq, allow the use of guarded corecursion to construct infinite values and proofs. Guarded corecursion is a form of recursion in which arbitrary recursive calls are allowed, as long as they are guarded by a coinductive constructor. Guardedness ensures that programs are productive, i.e. that every finite prefix of an infinite value can be computed in finite time. However, many productive programs are not guarded, and it can be nontrivial to put them in guarded form. This paper gives a method for turning a productive program into a guarded program. The method amounts to defining a problem-specific language as a data type, writing the program in the problem-specific language, and writing a guarded interpreter for this language.


General Recursion and Formal Topology

Abstract: It is well known that general recursion cannot be expressed within Martin-Loef's type theory and various approaches have been proposed to overcome this problem still maintaining the termination of the computation of the typable terms. In this work we propose a new approach to this problem based on the use of inductively generated formal topologies.


Termination Casts: A Flexible Approach to Termination with General Recursion

Abstract: This paper proposes a type-and-effect system called Teqt, which distinguishes terminating terms and total functions from possibly diverging terms and partial functions, for a lambda calculus with general recursion and equality types. The central idea is to include a primitive type-form "Terminates t", expressing that term t is terminating; and then allow terms t to be coerced from possibly diverging to total, using a proof of Terminates t. We call such coercions termination casts, and show how to implement terminating recursion using them. For the meta-theory of the system, we describe a translation from Teqt to a logical theory of termination for general recursive, simply typed functions. Every typing judgment of Teqt is translated to a theorem expressing the appropriate termination property of the computational part of the Teqt term.


Join-Reachability Problems in Directed Graphs

Abstract: For a given collection G of directed graphs we define the join-reachability graph of G, denoted by J(G), as the directed graph that, for any pair of vertices a and b, contains a path from a to b if and only if such a path exists in all graphs of G. Our goal is to compute an efficient representation of J(G). In particular, we consider two versions of this problem. In the explicit version we wish to construct the smallest join-reachability graph for G. In the implicit version we wish to build an efficient data structure (in terms of space and query time) such that we can report fast the set of vertices that reach a query vertex in all graphs of G. This problem is related to the well-studied reachability problem and is motivated by emerging applications of graph-structured databases and graph algorithms. We consider the construction of join-reachability structures for two graphs and develop techniques that can be applied to both the explicit and the implicit problem. First we present optimal and near-optimal structures for paths and trees. Then, based on these results, we provide efficient structures for planar graphs and general directed graphs.


Experience in applying remote technology in the secondary education institutions in Russia, located in rural areas (From the experience of Podolsky municipal district schools)

Abstract: This article examines the experience of distance education technologies in Podolsky municipal district, Moscow region.


Robust and MaxMin Optimization under Matroid and Knapsack Uncertainty Sets

Abstract: Consider the following problem: given a set system (U,I) and an edge-weighted graph G = (U, E) on the same universe U, find the set A in I such that the Steiner tree cost with terminals A is as large as possible: "which set in I is the most difficult to connect up?" This is an example of a max-min problem: find the set A in I such that the value of some minimization (covering) problem is as large as possible. In this paper, we show that for certain covering problems which admit good deterministic online algorithms, we can give good algorithms for max-min optimization when the set system I is given by a p-system or q-knapsacks or both. This result is similar to results for constrained maximization of submodular functions. Although many natural covering problems are not even approximately submodular, we show that one can use properties of the online algorithm as a surrogate for submodularity. Moreover, we give stronger connections between max-min optimization and two-stage robust optimization, and hence give improved algorithms for robust versions of various covering problems, for cases where the uncertainty sets are given by p-systems and q-knapsacks.


Shortest Paths with Pairwise-Distinct Edge Labels: Finding Biochemical Pathways in Metabolic Networks

Abstract: A problem studied in Systems Biology is how to find shortest paths in metabolic networks. Unfortunately, simple (i.e., graph theoretic) shortest paths do not properly reflect biochemical facts. An approach to overcome this issue is to use edge labels and search for paths with distinct labels. In this paper, we show that such biologically feasible shortest paths are hard to compute. Moreover, we present solutions to find such paths in networks in reasonable time.


Work-stealing for mixed-mode parallelism by deterministic team-building

Abstract: We show how to extend classical work-stealing to deal also with data parallel tasks that can require any number of threads r >= 1 for their execution. We explain in detail the so introduced idea of work-stealing with deterministic team-building which in a natural way generalizes classical work-stealing. A prototype C++ implementation of the generalized work-stealing algorithm has been given and is briefly described. Building on this, a serious, well-known contender for a best parallel Quicksort algorithm has been implemented, which naturally relies on both task and data parallelism. For instance, sorting 2^27-1 randomly generated integers we could improve the speed-up from 5.1 to 8.7 on a 32-core Intel Nehalem EX system, being consistently better than the tuned, task-parallel Cilk++ system.


Power-Rate Allocation in DS/CDMA Based on Discretized Verhulst Equilibrium

Abstract: This paper proposes to extend the discrete Verhulst power equilibrium approach, previously suggested in [1], to the power-rate optimal allocation problem. Multirate users associated to different types of traffic are aggregated to distinct user' classes, with the assurance of minimum rate allocation per user and QoS. Herein, Verhulst power allocation algorithm was adapted to the single-input-single-output DS/CDMA jointly power-rate control problem. The analysis was carried out taking into account the convergence time, quality of solution, in terms of the normalized squared error (NSE), when compared with the analytical solution based on interference matrix inverse, and computational complexity. Numerical results demonstrate the validity of the proposed resource allocation methodology.


Timed Game Abstraction of Control Systems

Abstract: This paper proposes a method for abstracting control systems by timed game automata, and is aimed at obtaining automatic controller synthesis. The proposed abstraction is based on partitioning the state space of a control system using positive and negative invariant sets, generated by Lyapunov functions. This partitioning ensures that the vector field of the control system is transversal to the facets of the cells, which induces some desirable properties of the abstraction. To allow a rich class of control systems to be abstracted, the update maps of the timed game automaton are extended. Conditions on the partitioning of the state space and the control are set up to obtain sound abstractions. Finally, an example is provided to demonstrate the method applied to a control problem related to navigation.


XSB: Extending Prolog with Tabled Logic Programming

Abstract: The paradigm of Tabled Logic Programming (TLP) is now supported by a number of Prolog systems, including XSB, YAP Prolog, B-Prolog, Mercury, ALS, and Ciao. The reasons for this are partly theoretical: tabling ensures termination and optimal known complexity for queries to a large class of programs. However the overriding reasons are practical. TLP allows sophisticated programs to be written concisely and efficiently, especially when mechanisms such as tabled negation and call and answer subsumption are supported. As a result TLP has now been used in a variety of applications from program analysis to querying over the semantic web. This paper provides a survey of TLP and its applications as implemented in XSB Prolog, along with discussion of how XSB supports tabling with dynamically changing code, and in a multi-threaded environment.


A Relation between the Protocol Partition Number and the Quasi-Additive Bound

Abstract: In this note, we show that the linear programming for computing the quasi-additive bound of the formula size of a Boolean function presented by Ueno [MFCS'10] is equivalent to the dual problem of the linear programming relaxation of an integer programming for computing the protocol partition number. Together with the result of Ueno [MFCS'10], our results imply that there exists no gap between our integer programming for computing the protocol partition number and its linear programming relaxation.


Public Announcements in Strategic Games with Arbitrary Strategy Sets

Abstract: In [Van Benthem 2007] the concept of a public announcement is used to study the effect of the iterated elimination of strictly dominated strategies. We offer a simple generalisation of this approach to cover arbitrary strategic games and many optimality notions. We distinguish between announcements of optimality and announcements of rationality.


Texture feature extraction in the spatial-frequency domain for content-based image retrieval

Abstract: The advent of large scale multimedia databases has led to great challenges in content-based image retrieval (CBIR). Even though CBIR is considered an emerging field of research, however it constitutes a strong background for new methodologies and systems implementations. Therefore, many research contributions are focusing on techniques enabling higher image retrieval accuracy while preserving low level of computational complexity. Image retrieval based on texture features is receiving special attention because of the omnipresence of this visual feature in most real-world images. This paper highlights the state-of-the-art and current progress relevant to texture-based image retrieval and spatial-frequency image representations. In particular, it gives an overview of statistical methodologies and techniques employed for texture feature extraction using most popular spatial-frequency image transforms, namely discrete wavelets, Gabor wavelets, dual-tree complex wavelet and contourlets. Indications are also given about used similarity measurement functions and most important achieved results.


Exploring Grid Polygons Online

Abstract: We investigate the exploration problem of a short-sighted mobile robot moving in an unknown cellular room. To explore a cell, the robot must enter it. Once inside, the robot knows which of the 4 adjacent cells exist and which are boundary edges. The robot starts from a specified cell adjacent to the room's outer wall; it visits each cell, and returns to the start. Our interest is in a short exploration tour; that is, in keeping the number of multiple cell visits small. For abitrary environments containing no obstacles we provide a strategy producing tours of length S <= C + 1/2 E - 3, and for environments containing obstacles we provide a strategy, that is bound by S <= C + 1/2 E + 3H + WCW - 2, where C denotes the number of cells-the area-, E denotes the number of boundary edges-the perimeter-, and H is the number of obstacles, and WCW is a measure for the sinuosity of the given environment.


Matrix Insertion-Deletion Systems

Abstract: In this article, we consider for the first time the operations of insertion and deletion working in a matrix controlled manner. We show that, similarly as in the case of context-free productions, the computational power is strictly increased when using a matrix control: computational completeness can be obtained by systems with insertion or deletion rules involving at most two symbols in a contextual or in a context-free manner and using only binary matrices.


Exploring Simple Triangular and Hexagonal Grid Polygons Online

Abstract: We investigate the online exploration problem (aka covering) of a short-sighted mobile robot moving in an unknown cellular environment with hexagons and triangles as types of cells. To explore a cell, the robot must enter it. Once inside, the robot knows which of the 3 or 6 adjacent cells exist and which are boundary edges. The robot's task is to visit every cell in the given environment and to return to the start. Our interest is in a short exploration tour; that is, in keeping the number of multiple cell visits small. For arbitrary environments containing no obstacles we provide a strategy producing tours of length S <= C + 1/4 E - 2.5 for hexagonal grids, and S <= C + E - 4 for triangular grids. C denotes the number of cells-the area-, E denotes the number of boundary edges-the perimeter-of the given environment. Further, we show that our strategy is 4/3-competitive in both types of grids, and we provide lower bounds of 14/13 for hexagonal grids and 7/6 for triangular grids.


Optimal competitive online ray search with an error-prone robot

Abstract: We consider the problem of finding a door along a wall with a blind robot that neither knows the distance to the door nor the direction towards of the door. This problem can be solved with the well-known doubling strategy yielding an optimal competitive factor of 9 with the assumption that the robot does not make any errors during its movements. We study the case that the robot's movement is erroneous. In this case the doubling strategy is no longer optimal. We present optimal competitive strategies that take the error assumption into account. The analysis technique can be applied to different error models.


No-Break Dynamic Defragmentation of Reconfigurable Devices

Abstract: We propose a new method for defragmenting the module layout of a reconfigurable device, enabled by a novel approach for dealing with communication needs between relocated modules and with inhomogeneities found in commonly used FPGAs. Our method is based on dynamic relocation of module positions during runtime, with only very little reconfiguration overhead; the objective is to maximize the length of contiguous free space that is available for new modules. We describe a number of algorithmic aspects of good defragmentation, and present an optimization method based on tabu search. Experimental results indicate that we can improve the quality of module layout by roughly 50 % over static layout. Among other benefits, this improvement avoids unnecessary rejections of modules


Proceedings International Workshop on Strategies in Rewriting, Proving, and Programming

Abstract: This volume contains selected papers from the proceedings of the First International Workshop on Strategies in Rewriting, Proving, and Programming (IWS 2010), which was held on July 9, 2010, in Edinburgh, UK. Strategies are ubiquitous in programming languages, automated deduction and reasoning systems. In the two communities of Rewriting and Programming on one side, and of Deduction and Proof engines (Provers, Assistants, Solvers) on the other side, workshops have been launched to make progress towards a deeper understanding of the nature of strategies, their descriptions, their properties, and their usage, in all kinds of computing and reasoning systems. Since more recently, strategies are also playing an important role in rewrite-based programming languages, verification tools and techniques like SAT/SMT engines or termination provers. Moreover strategies have come to be viewed more generally as expressing complex designs for control in computing, modeling, proof search, program transformation, and access control. IWS 2010 was organized as a satellite workshop of FLoC 2010. FLoC 2010 provided an excellent opportunity to foster exchanges between the communities of Rewriting and Programming on one side, and of Deduction and Proof engines on the other side. IWS2010 was a joint follow-up of two series of worshops, held since 1997: the Strategies workshops held by the CADE-IJCAR community and the Workshops on Reduction Strategies (WRS) held by the RTA-RDP community.


Quasirandom Rumor Spreading

Abstract: We propose and analyze a quasirandom analogue of the classical push model for disseminating information in networks ("randomized rumor spreading"). In the classical model, in each round each informed vertex chooses a neighbor at random and informs it, if it was not informed before. It is known that this simple protocol succeeds in spreading a rumor from one vertex to all others within O(log n) rounds on complete graphs, hypercubes, random regular graphs, Erdos-Renyi random graph and Ramanujan graphs with probability 1-o(1). In the quasirandom model, we assume that each vertex has a (cyclic) list of its neighbors. Once informed, it starts at a random position on the list, but from then on informs its neighbors in the order of the list. Surprisingly, irrespective of the orders of the lists, the above-mentioned bounds still hold. In some cases, even better bounds than for the classical model can be shown.


Computing Differential Equations for Integrals Associated to Smooth Fano Polytopes

Abstract: We give an approximate algorithm of computing holonomic systems of linear differential equations for definite integrals with parameters. We show that this algorithm gives a correct answer in finite steps, but we have no general stopping condition. We apply the approximate method to find differential equations for integrals associated to smooth Fano polytopes. They are interested in the study of K3 surfaces and the toric mirror symmetry. In this class of integrals, we can apply Stienstra's rank formula to our algorithm, which gives a stopping condition of the approximate algorithm.


Quasirandom Rumor Spreading: An Experimental Analysis

Abstract: We empirically analyze two versions of the well-known "randomized rumor spreading" protocol to disseminate a piece of information in networks. In the classical model, in each round each informed node informs a random neighbor. In the recently proposed quasirandom variant, each node has a (cyclic) list of its neighbors. Once informed, it starts at a random position of the list, but from then on informs its neighbors in the order of the list. While for sparse random graphs a better performance of the quasirandom model could be proven, all other results show that, independent of the structure of the lists, the same asymptotic performance guarantees hold as for the classical model. In this work, we compare the two models experimentally. This not only shows that the quasirandom model generally is faster, but also that the runtime is more concentrated around the mean. This is surprising given that much fewer random bits are used in the quasirandom process. These advantages are also observed in a lossy communication model, where each transmission does not reach its target with a certain probability, and in an asynchronous model, where nodes send at random times drawn from an exponential distribution. We also show that typically the particular structure of the lists has little influence on the efficiency.


GMRES-based multigrid for the complex scaled preconditoner for the indefinite Helmholtz equation

Abstract: Multigrid preconditioners and solvers for the indefinite Helmholtz equation suffer from non-stability of the stationary smoothers due to the indefinite spectrum of the operator. In this paper we explore GMRES as a replacement for the stationary smoothers of the standard multigrid method. This results in a robust and efficient solver for a complex shifted or stretched Helmholtz problem that can be used as a preconditioner. Very few GMRES iterations are required on each level to build a good multigrid method. The convergence behavior is compared to a theoretically derived stable polynomial smoother. We test this method on some benchmark problems and report on the observed convergence behavior.


Analysis of Computer Science Communities Based on DBLP

Abstract: It is popular nowadays to bring techniques from bibliometrics and scientometrics into the world of digital libraries to analyze the collaboration patterns and explore mechanisms which underlie community development. In this paper we use the DBLP data to investigate the author's scientific career and provide an in-depth exploration of some of the computer science communities. We compare them in terms of productivity, population stability and collaboration trends.Besides we use these features to compare the sets of topranked conferences with their lower ranked counterparts.


Extending B\"uchi Automata with Constraints on Data Values

Abstract: Recently data trees and data words have received considerable amount of attention in connection with XML reasoning and system verification. These are trees or words that, in addition to labels from a finite alphabet, carry data values from an infinite alphabet (data). In general it is rather hard to obtain logics for data words and trees that are sufficiently expressive, but still have reasonable complexity for the satisfiability problem. In this paper we extend and study the notion of B\"uchi automata for omega-words with data. We prove that the emptiness problem for such extension is decidable in elementary complexity. We then apply our result to show the decidability of two kinds of logics for omega-words with data: the two-variable fragment of first-order logic and some extensions of classical linear temporal logic for omega-words with data.


Generalized Linear Weights for Sharing Credits Among Multiple Authors

Abstract: Assignment of weights to multiple authors of a paper is a challenging task due to its dependence on the conventions that may be different among different fields of research and research groups. In this paper, we describe a scheme for assignment of weights to multiple authors of a paper. In our scheme, weights are assigned in a linearly decreasing/increasing fashion depending upon the weight decrement/increment parameter. We call our scheme Arithmetic: Type-2 scheme as the weights follow an arithmetic series. We analyze the proposed weight assignment scheme and compare it with the existing schemes such as equal, arithmetic, geometric, and harmonic. We argue that the a positional weight assignment scheme, called arithmetic scheme, which we refer to Arithmetic: Type-1 in this paper, and the equal weight assignment scheme can be treated as special cases of the proposed Arithmetic: Type-2 scheme.


A contribution to the conditioning of the total least squares problem

Abstract: We derive closed formulas for the condition number of a linear function of the total least squares solution. Given an over determined linear system Ax=b, we show that this condition number can be computed using the singular values and the right singular vectors of [A,b] and A. We also provide an upper bound that requires the computation of the largest and the smallest singular value of [A,b] and the smallest singular value of A. In numerical examples, we compare these values and the resulting forward error bounds with existing error estimates.


Contents of COMP6411 Summer 2010 Final Reports on Comparative Studies of Programming Languages

Abstract: This index covers the lecture notes and the final course project reports for COMP6411 Summer 2010 at Concordia University, Montreal, Canada, Comparative Study of Programming Languages by 4 teams trying compare a set of common criteria and their applicability to about 10 distinct programming languages, where 5 language choices were provided by the instructor and five were picked by each team and each student individually compared two of the 10 and then the team did a summary synthesis across all 10 languages. Their findings are posted here for further reference, comparative studies, and analysis.


Ontology-based Queries over Cancer Data

Abstract: The ever-increasing amount of data in biomedical research, and in cancer research in particular, needs to be managed to support efficient data access, exchange and integration. Existing software infrastructures, such caGrid, support access to distributed information annotated with a domain ontology. However, caGrid's current querying functionality depends on the structure of individual data resources without exploiting the semantic annotations. In this paper, we present the design and development of an ontology-based querying functionality that consists of: the generation of OWL2 ontologies from the underlying data resources metadata and a query rewriting and translation process based on reasoning, which converts a query at the domain ontology level into queries at the software infrastructure level. We present a detailed analysis of our approach as well as an extensive performance evaluation. While the implementation and evaluation was performed for the caGrid infrastructure, the approach could be applicable to other model and metadata-driven environments for data sharing.


Mining Multi-Level Frequent Itemsets under Constraints

Abstract: Mining association rules is a task of data mining, which extracts knowledge in the form of significant implication relation of useful items (objects) from a database. Mining multilevel association rules uses concept hierarchies, also called taxonomies and defined as relations of type 'is-a' between objects, to extract rules that items belong to different levels of abstraction. These rules are more useful, more refined and more interpretable by the user. Several algorithms have been proposed in the literature to discover the multilevel association rules. In this article, we are interested in the problem of discovering multi-level frequent itemsets under constraints, involving the user in the research process. We proposed a technique for modeling and interpretation of constraints in a context of use of concept hierarchies. Three approaches for discovering multi-level frequent itemsets under constraints were proposed and discussed: Basic approach, "Test and Generate" approach and Pruning based Approach.


Strategic programming on graph rewriting systems

Abstract: We describe a strategy language to control the application of graph rewriting rules, and show how this language can be used to write high-level declarative programs in several application areas. This language is part of a graph-based programming tool built within the port-graph transformation and visualisation environment PORGY.


Properties of Exercise Strategies

Abstract: Mathematical learning environments give domain-specific and immediate feedback to students solving a mathematical exercise. Based on a language for specifying strategies, we have developed a feedback framework that automatically calculates semantically rich feedback. We offer this feedback functionality to mathematical learning environments via a set of web services. Feedback is only effective when it is precise and to the point. The tests we have performed give some confidence about the correctness of our feedback services. To increase confidence in our services, we explicitly specify the properties our feedback services should satisfy, and, if possible, prove them correct. For this, we give a formal description of the concepts used in our feedback framework services. The formalisation allows us to reason about these concepts, and to state a number of desired properties of the concepts. Our feedback services use exercise descriptions for their instances on domains such as logic, algebra, and linear algebra. We formulate requirements these domain descriptions should satisfy for the feedback services to react as expected.


Termination of Rewriting with and Automated Synthesis of Forbidden Patterns

Abstract: We introduce a modified version of the well-known dependency pair framework that is suitable for the termination analysis of rewriting under forbidden pattern restrictions. By attaching contexts to dependency pairs that represent the calling contexts of the corresponding recursive function calls, it is possible to incorporate the forbidden pattern restrictions in the (adapted) notion of dependency pair chains, thus yielding a sound and complete approach to termination analysis. Building upon this contextual dependency pair framework we introduce a dependency pair processor that simplifies problems by analyzing the contextual information of the dependency pairs. Moreover, we show how this processor can be used to synthesize forbidden patterns suitable for a given term rewriting system on-the-fly during the termination analysis.


Loops under Strategies ... Continued

Abstract: While there are many approaches for automatically proving termination of term rewrite systems, up to now there exist only few techniques to disprove their termination automatically. Almost all of these techniques try to find loops, where the existence of a loop implies non-termination of the rewrite system. However, most programming languages use specific evaluation strategies, whereas loop detection techniques usually do not take strategies into account. So even if a rewrite system has a loop, it may still be terminating under certain strategies. Therefore, our goal is to develop decision procedures which can determine whether a given loop is also a loop under the respective evaluation strategy. In earlier work, such procedures were presented for the strategies of innermost, outermost, and context-sensitive evaluation. In the current paper, we build upon this work and develop such decision procedures for important strategies like leftmost-innermost, leftmost-outermost, (max-)parallel-innermost, (max-)parallel-outermost, and forbidden patterns (which generalize innermost, outermost, and context-sensitive strategies). In this way, we obtain the first approach to disprove termination under these strategies automatically.


Image Sterilization to Prevent LSB-based Steganographic Transmission

Abstract: Sterilization is a very popular word used in biomedical testing (like removal of all microorganisms on surface of an article or in fluid using appropriate chemical products). Motivated by this biological analogy, we, for the first time, introduce the concept of sterilization of an image, i.e., removing any steganographic information embedded in the image. Experimental results show that our technique succeeded in sterilizing around 76% to 91% of stego pixels in an image on average, where data is embedded using LSB-based steganography.


The El-Gamal AA_{\beta} Public Key Cryptosystem - A new approach utilizing the subset sum problem in designing an asymmetric cryptosystem

Abstract: The El-Gamal AA_{\beta} Public Key Cryptosystem is a new asymmetric cryptosystem based on the piecewise AA_{\beta}-function. The AA_{\beta}-function which is essentially a one way Boolean function was motivated by the squaring and multiplying process while computing g^a (mod p) in the Diffie Hellman key exchange procedure and also computing C \equiv M^e (mod N) and M \equiv C^d (mod N) in the RSA cryptosystem. It was also motivated by the add and double point operation E=kG in the elliptic curve cryptosystem. The hard mathematical problem surrounding this newly designed asymmetric cryptosystem is the NP-complete problem known as the subset sum problem. The El-Gamal AA_{\beta} Public Key Cryptosystem mimics the El-Gamal Cryptosystem and the Elliptic Curve Cryptosystem by sending a two parameter ciphertext to the recipient.


Symmetry Breaking with Polynomial Delay

Abstract: A conservative class of constraint satisfaction problems CSPs is a class for which membership is preserved under arbitrary domain reductions. Many well-known tractable classes of CSPs are conservative. It is well known that lexleader constraints may significantly reduce the number of solutions by excluding symmetric solutions of CSPs. We show that adding certain lexleader constraints to any instance of any conservative class of CSPs still allows us to find all solutions with a time which is polynomial between successive solutions. The time is polynomial in the total size of the instance and the additional lexleader constraints. It is well known that for complete symmetry breaking one may need an exponential number of lexleader constraints. However, in practice, the number of additional lexleader constraints is typically polynomial number in the size of the instance. For polynomially many lexleader constraints, we may in general not have complete symmetry breaking but polynomially many lexleader constraints may provide practically useful symmetry breaking -- and they sometimes exclude super-exponentially many solutions. We prove that for any instance from a conservative class, the time between finding successive solutions of the instance with polynomially many additional lexleader constraints is polynomial even in the size of the instance without lexleaderconstraints.


Automated Symbolic Analysis of ARBAC-Policies (Extended Version)

Abstract: One of the most widespread framework for the management of access-control policies is Administrative Role Based Access Control (ARBAC). Several automated analysis techniques have been proposed to help maintaining desirable security properties of ARBAC policies. One limitation of many available techniques is that the sets of users and roles are bounded. In this paper, we propose a symbolic framework to overcome this difficulty. We design an automated security analysis technique, parametric in the number of users and roles, by adapting recent methods for model checking infinite state systems that use first-order logic and state-of-the-art theorem proving techniques. Preliminary experiments with a prototype implementations seem to confirm the scalability of our technique.


The Ethics of Robotics

Abstract: The three laws of Robotics first appeared together in Isaac Asimov's story 'Runaround' after being mentioned in some form or the other in previous works by Asimov. These three laws commonly known as the three laws of robotics are the earliest forms of depiction for the needs of ethics in Robotics. In simplistic language Isaac Asimov is able to explain what rules a robot must confine itself to in order to maintain societal sanctity. However, even though they are outdated they still represent some of our innate fears which are beginning to resurface in present day 21st Century. Our society is on the advent of a new revolution; a revolution led by advances in Computer Science, Artificial Intelligence & Nanotechnology. Some of our advances have been so phenomenal that we surpassed what was predicted by the Moore's law. With these advancements comes the fear that our future may be at the mercy of these androids. Humans today are scared that we, ourselves, might create something which we cannot control. We may end up creating something which can not only learn much faster than anyone of us can, but also evolve faster than what the theory of evolution has allowed us to. The greatest fear is not only that we might lose our jobs to these intelligent beings, but that these beings might end up replacing us at the top of the cycle. The public hysteria has been heightened more so by a number of cultural works which depict annihilation of the human race by robots. Right from Frankenstein to I, Robot mass media has also depicted such issues. This paper is an effort to understand the need for ethics in Robotics or simply termed as Roboethics. This is achieved by the study of artificial beings and the thought being put behind them. By the end of the paper, however, it is concluded that there isn't a need for ethical robots but more so ever a need for ethical roboticists.


Manipulating Multistage Interconnection Networks Using Fundamental Arrangements

Abstract: Optimizing interconnection networks is a prime object in switching schemes. In this work the authors present a novel approach for obtaining a required channel arrangement in a multi-stage interconnection network, using a new concept - a fundamental arrangement. The fundamental arrangement is an initial N-1 stage switch arrangement that allows obtaining any required output channel arrangement given an input arrangement, using N/2 binary switches at each stage. The paper demonstrates how a fundamental arrangement can be achieved and how, once this is done, any required arrangement may be obtained within 2(N-1) steps.


Free and Open-Source Software is not an Emerging Property but Rather the Result of Studied Design

Abstract: Free and open source software (FOSS) is considered by many, along with Wikipedia, the proof of an ongoing paradigm shift from hierarchically-managed and market-driven production of knowledge to heterarchical, collaborative and commons-based production styles. In such perspective, it has become common place to refer to FOSS as a manifestation of collective intelligence where deliverables and artefacts emerge by virtue of mere cooperation, with no need for supervising leadership. The paper argues that this assumption is based on limited understanding of the software development process, and may lead to wrong conclusions as to the potential of peer production. The development of a less than trivial piece of software, irrespective of whether it be FOSS or proprietary, is a complex cooperative effort requiring the participation of many (often thousands of) individuals. A subset of the participants always play the role of leading system and subsystem designers, determining architecture and functionality; the rest of the people work "underneath" them in a logical, functional sense. While new and powerful forces, including FOSS, are clearly at work in the post-industrial, networked econ-omy, the currently ingenuous stage of research in the field of collective intelligence and networked cooperation must give way to a deeper level of consciousness, which requires an understanding of the software development process.


Non-negative Weighted #CSPs: An Effective Complexity Dichotomy

Abstract: We prove a complexity dichotomy theorem for all non-negative weighted counting Constraint Satisfaction Problems (CSP). This caps a long series of important results on counting problems including unweighted and weighted graph homomorphisms and the celebrated dichotomy theorem for unweighted #CSP. Our dichotomy theorem gives a succinct criterion for tractability. If a set F of constraint functions satisfies the criterion, then the counting CSP problem defined by F is solvable in polynomial time; if it does not satisfy the criterion, then the problem is #P-hard. We furthermore show that the question of whether F satisfies the criterion is decidable in NP. Surprisingly, our tractability criterion is simpler than the previous criteria for the more restricted classes of problems, although when specialized to those cases, they are logically equivalent. Our proof mainly uses Linear Algebra, and represents a departure from Universal Algebra, the dominant methodology in recent years.


Bounds on the maximum multiplicity of some common geometric graphs

Abstract: We obtain new lower and upper bounds for the maximum multiplicity of some weighted and, respectively, non-weighted common geometric graphs drawn on n points in the plane in general position (with no three points collinear): perfect matchings, spanning trees, spanning cycles (tours), and triangulations. (i) We present a new lower bound construction for the maximum number of triangulations a set of n points in general position can have. In particular, we show that a generalized double chain formed by two almost convex chains admits {\Omega}(8.65^n) different triangulations. This improves the bound {\Omega}(8.48^n) achieved by the double zig-zag chain configuration studied by Aichholzer et al. (ii) We present a new lower bound of {\Omega}(12.00^n) for the number of non-crossing spanning trees of the double chain composed of two convex chains. The previous bound, {\Omega}(10.42^n), stood unchanged for more than 10 years. (iii) Using a recent upper bound of 30^n for the number of triangulations, due to Sharir and Sheffer, we show that n points in the plane in general position admit at most O(68.62^n) non-crossing spanning cycles. (iv) We derive lower bounds for the number of maximum and minimum weighted geometric graphs (matchings, spanning trees, and tours). We show that the number of shortest non-crossing tours can be exponential in n. Likewise, we show that both the number of longest non-crossing tours and the number of longest non-crossing perfect matchings can be exponential in n. Moreover, we show that there are sets of n points in convex position with an exponential number of longest non-crossing spanning trees. For points in convex position we obtain tight bounds for the number of longest and shortest tours. We give a combinatorial characterization of the longest tours, which leads to an O(nlog n) time algorithm for computing them.


Dynamic Scheduling of Skippable Periodic Tasks with Energy Efficiency in Weakly Hard Real-Time System

Abstract: Energy consumption is a critical design issue in real-time systems, especially in battery- operated systems. Maintaining high performance, while extending the battery life between charges is an interesting challenge for system designers. Dynamic Voltage Scaling (DVS) allows a processor to dynamically change speed and voltage at run time, thereby saving energy by spreading run cycles into idle time. Knowing when to use full power and when not, requires the cooperation of the operating system scheduler. Usually, higher processor voltage and frequency leads to higher system throughput while energy reduction can be obtained using lower voltage and frequency. Instead of lowering processor voltage and frequency as much as possible, energy efficient real-time scheduling adjusts voltage and frequency according to some optimization criteria, such as low energy consumption or high throughput, while it meets the timing constraints of the real-time tasks. As the quantity and functional complexity of battery powered portable devices continues to raise, energy efficient design of such devices has become increasingly important. Many real-time scheduling algorithms have been developed recently to reduce energy consumption in the portable devices that use DVS capable processors. Three algorithms namely Red Tasks Only (RTO), Blue When Possible (BWP) and Red as Late as Possible (RLP) are proposed in the literature to schedule the real-time tasks in Weakly-hard real-time systems. This paper proposes optimal slack management algorithms to make the above existing weakly hard real-time scheduling algorithms energy efficient using DVS and DPD techniques.


Fast and Tiny Structural Self-Indexes for XML

Abstract: XML document markup is highly repetitive and therefore well compressible using dictionary-based methods such as DAGs or grammars. In the context of selectivity estimation, grammar-compressed trees were used before as synopsis for structural XPath queries. Here a fully-fledged index over such grammars is presented. The index allows to execute arbitrary tree algorithms with a slow-down that is comparable to the space improvement. More interestingly, certain algorithms execute much faster over the index (because no decompression occurs). E.g., for structural XPath count queries, evaluating over the index is faster than previous XPath implementations, often by two orders of magnitude. The index also allows to serialize XML results (including texts) faster than previous systems, by a factor of ca. 2-3. This is due to efficient copy handling of grammar repetitions, and because materialization is totally avoided. In order to compare with twig join implementations, we implemented a materializer which writes out pre-order numbers of result nodes, and show its competitiveness.


Looking for plausibility

Abstract: In the interpretation of experimental data, one is actually looking for plausible explanations. We look for a measure of plausibility, with which we can compare different possible explanations, and which can be combined when there are different sets of data. This is contrasted to the conventional measure for probabilities as well as to the proposed measure of possibilities. We define what characteristics this measure of plausibility should have. In getting to the conception of this measure, we explore the relation of plausibility to abductive reasoning, and to Bayesian probabilities. We also compare with the Dempster-Schaefer theory of evidence, which also has its own definition for plausibility. Abduction can be associated with biconditionality in inference rules, and this provides a platform to relate to the Collins-Michalski theory of plausibility. Finally, using a formalism for wiring logic onto Hopfield neural networks, we ask if this is relevant in obtaining this measure.


Business Mereology: Imaginative Definitions of Insourcing and Outsourcing Transformations

Abstract: Outsourcing, the passing on of tasks by organizations to other organizations, often including the personnel and means to perform these tasks, has become an important IT-business strategy over the past decades. We investigate imaginative definitions for outsourcing relations and outsourcing transformations. Abstract models of an extreme and unrealistic simplicity are considered in order to investigate possible definitions of outsourcing. Rather than covering all relevant practical cases an imaginative definition of a concept provides obvious cases of its instantiation from which more refined or liberal definitions may be derived. A definition of outsourcing induces to a complementary definition of insourcing. Outsourcing and insourcing have more complex variations in which multiple parties are involved. All of these terms both refer to state transformations and to state descriptions pertaining to the state obtained after such transformations. We make an attempt to disambiguate the terminology in that respect and we make an attempt to characterize the general concept of sourcing which captures some representative cases. Because mereology is the most general theory of parthood relations we coin business mereology as the general theory in business studies which concerns the full variety of sourcing relations and transformations.


Software Effort Estimation with Ridge Regression and Evolutionary Attribute Selection

Abstract: Software cost estimation is one of the prerequisite managerial activities carried out at the software development initiation stages and also repeated throughout the whole software life-cycle so that amendments to the total cost are made. In software cost estimation typically, a selection of project attributes is employed to produce effort estimations of the expected human resources to deliver a software product. However, choosing the appropriate project cost drivers in each case requires a lot of experience and knowledge on behalf of the project manager which can only be obtained through years of software engineering practice. A number of studies indicate that popular methods applied in the literature for software cost estimation, such as linear regression, are not robust enough and do not yield accurate predictions. Recently the dual variables Ridge Regression (RR) technique has been used for effort estimation yielding promising results. In this work we show that results may be further improved if an AI method is used to automatically select appropriate project cost drivers (inputs) for the technique. We propose a hybrid approach combining RR with a Genetic Algorithm, the latter evolving the subset of attributes for approximating effort more accurately. The proposed hybrid cost model has been applied on a widely known high-dimensional dataset of software project samples and the results obtained show that accuracy may be increased if redundant attributes are eliminated.


DD-EbA: An algorithm for determining the number of neighbors in cost estimation by analogy using distance distributions

Abstract: Case Based Reasoning and particularly Estimation by Analogy, has been used in a number of problem-solving areas, such as cost estimation. Conventional methods, despite the lack of a sound criterion for choosing nearest projects, were based on estimation using a fixed and predetermined number of neighbors from the entire set of historical instances. This approach puts boundaries to the estimation ability of such algorithms, for they do not take into consideration that every project under estimation is unique and requires different handling. The notion of distributions of distances together with a distance metric for distributions help us to adapt the proposed method (we call it DD-EbA) each time to a specific case that is to be estimated without loosing in prediction power or computational cost. The results of this paper show that the proposed technique achieves the above idea in a very efficient way.


Algebraic Notions of Termination

Abstract: Five algebraic notions of termination are formalised, analysed and compared: wellfoundedness or Noetherity, L\"ob's formula, absence of infinite iteration, absence of divergence and normalisation. The study is based on modal semirings, which are additively idempotent semirings with forward and backward modal operators. To model infinite behaviours, idempotent semirings are extended to divergence semirings, divergence Kleene algebras and omega algebras. The resulting notions and techniques are used in calculational proofs of classical theorems of rewriting theory. These applications show that modal semirings are powerful tools for reasoning algebraically about the finite and infinite dynamics of programs and transition systems.


Finding of k in Fagin's R. Theorem 24

Abstract: By using of analytical multi-logic expresses in conjunction with non-deterministic Turing machine the proposition was proved that algorithm of deterministic Turing counter machine of polynomial time complexity can be decreased to the algorithm of linear time complexity in non-deterministic Turing counter machine. Furthermore, it was shown that existence of reduction of polynomial time complexity to the linear time complexity by switching from deterministic to non-deterministic Turing machine for string recognition imply P equals to NP. Analytical generation functions of higher order logic were used for finding of k value in Fagin's R. Theorem 24.


SAPFOCS: a metaheuristic based approach to part family formation problems in group technology

Abstract: This article deals with Part family formation problem which is believed to be moderately complicated to be solved in polynomial time in the vicinity of Group Technology (GT). In the past literature researchers investigated that the part family formation techniques are principally based on production flow analysis (PFA) which usually considers operational requirements, sequences and time. Part Coding Analysis (PCA) is merely considered in GT which is believed to be the proficient method to identify the part families. PCA classifies parts by allotting them to different families based on their resemblances in: (1) design characteristics such as shape and size, and/or (2) manufacturing characteristics (machining requirements). A novel approach based on simulated annealing namely SAPFOCS is adopted in this study to develop effective part families exploiting the PCA technique. Thereafter Taguchi's orthogonal design method is employed to solve the critical issues on the subject of parameters selection for the proposed metaheuristic algorithm. The adopted technique is therefore tested on 5 different datasets of size 5 {\times} 9 to 27 {\times} 9 and the obtained results are compared with C-Linkage clustering technique. The experimental results reported that the proposed metaheuristic algorithm is extremely effective in terms of the quality of the solution obtained and has outperformed C-Linkage algorithm in most instances.


Maximum Lifetime for Data Regeneration in Wireless Sensor Networks

Abstract: Robust distributed storage systems dedicated to wireless sensor networks utilize several nodes to redundantly store sensed data so that when some storage nodes fail, the sensed data can still be reconstructed. For the same level of redundancy, erasure coding based approaches are known to require less data storage space than replication methods. To maintain the same level of redundancy when one storage node fails, erasure coded data can be restored onto some other storage node by having this node download respective pieces from other live storage nodes. Previous works showed that the benefits in using erasure coding for robust storage over replication are made unappealing by the complication in regenerating lost data. More recent work has, however, shown that the bandwidth for erasure coded data can be further reduced by proposing Regenerating Coding, making erasure codes again desirable for robust data storage. But none of these works on regenerating coding consider how these codes will perform for data regeneration in wireless sensor networks. We therefore propose an analytical model to quantify the network lifetime gains of regenerating coding over classical schemes. We also propose a distributed algorithm, TROY, that determines which nodes and routes to use for data regeneration. Our analytical studies show that for certain topologies, TROY achieves maximum network lifetime. Our evaluation studies in real sensor network traces show that TROY achieves near optimal lifetime and performs better than baseline algorithms.


Universal regular autonomous asynchronous systems: omega-limit sets, invariance and basins of attraction

Abstract: The asynchronous systems are the non-deterministic real time-binary models of the asynchronous circuits from electrical engineering. Autonomy means that the circuits and their models have no input. Regularity means analogies with the dynamical systems, thus such systems may be considered to be the real time dynamical systems with a 'vector field' {\Phi}:{0,1}^2 \rightarrow {0,1}^2. Universality refers to the case when the state space of the system is the greatest possible in the sense of the inclusion. The purpose of the paper is that of defining, by analogy with the dynamical systems theory, the {\omega}-limit sets, the invariance and the basins of attraction of the universal regular autonomous asynchronous systems.


The model of the ideal rotary element of Morita

Abstract: Reversible computing is a concept reflecting physical reversibility. Until now several reversible systems have been investigated. In a series of papers Kenichi Morita defines the rotary element RE, that is a reversible logic element. By reversibility, he understands that 'every computation process can be traced backward uniquely from the end to the start. In other words, they are backward deterministic systems'. He shows that any reversible Turing machine can be realized as a circuit composed of RE's only. Our purpose in this paper is to use the asynchronous systems theory and the real time for the modeling of the ideal rotary element


On Elementary Loops of Logic Programs

Abstract: Using the notion of an elementary loop, Gebser and Schaub refined the theorem on loop formulas due to Lin and Zhao by considering loop formulas of elementary loops only. In this article, we reformulate their definition of an elementary loop, extend it to disjunctive programs, and study several properties of elementary loops, including how maximal elementary loops are related to minimal unfounded sets. The results provide useful insights into the stable model semantics in terms of elementary loops. For a nondisjunctive program, using a graph-theoretic characterization of an elementary loop, we show that the problem of recognizing an elementary loop is tractable. On the other hand, we show that the corresponding problem is {\sf coNP}-complete for a disjunctive program. Based on the notion of an elementary loop, we present the class of Head-Elementary-loop-Free (HEF) programs, which strictly generalizes the class of Head-Cycle-Free (HCF) programs due to Ben-Eliyahu and Dechter. Like an HCF program, an HEF program can be turned into an equivalent nondisjunctive program in polynomial time by shifting head atoms into the body.


Network Non-neutrality Debate: An Economic Analysis

Abstract: This paper studies the economic utilities and the quality of service (QoS) in a two-sided non-neutral market where Internet service providers (ISPs) charge content providers (CPs) for the content delivery. We propose new models on a two-sided market which involves a CP, an ISP, end users and advertisers. The CP may have either the subscription revenue model (charging end users) or the advertisement revenue model (charging advertisers). We formulate the interactions between the ISP and the CP as a noncooperative game problem for the former and an optimization problem for the latter. Our analysis shows that the revenue model of the CP plays a significant role in a non-neutral Internet. With the subscription model, both the ISP and the CP receive better (or worse) utilities as well as QoS in the presence of side payment at the same time. However, with the advertisement model, the side payment impedes the CP from investing on its contents.


Multiple-Source Multiple-Sink Maximum Flow in Directed Planar Graphs in $O(n^{1.5} \log n)$ Time

Abstract: We give an $O(n^{1.5} \log n)$ algorithm that, given a directed planar graph with arc capacities, a set of source nodes and a set of sink nodes, finds a maximum flow from the sources to the sinks.


Homophonic Coding Design for Communication Systems Employing the Encoding-Encryption Paradigm

Abstract: This paper addresses the design of a dedicated homophonic coding for a class of communication systems which, in order to provide both reliability and security, first encode the data before encrypting it, which is referred to as the encoding-encryption paradigm. The considered systems employ error-correction coding for reliability, a stream cipher for encryption, and homophonic coding to enhance the protection of the key used in the stream cipher, on which relies the security of all the system transmissions. This paper presents a security evaluation of such systems from a computational complexity point of view, which serves as a source for establishing dedicated homophonic code design criteria. The security evaluation shows that the computational complexity of recovering the secret key, given all the information an attacker could gather during passive attacks he can mount, is lower bounded by the complexity of the related LPN (Learning Parity in Noise) problem in both the average and worst case. This gives guidelines to construct a dedicated homophonic encoder which maximizes the complexity of the underlying LPN problem for a given encoding overhead. Finally, this paper proposes a generic homophonic coding strategy that fulfills the proposed design criteria and thus both enhances security while minimizing the induced overhead.


Near approximation of maximum weight matching through efficient weight reduction

Abstract: Let G be an edge-weighted hypergraph on n vertices, m edges of size \le s, where the edges have real weights in an interval [1,W]. We show that if we can approximate a maximum weight matching in G within factor alpha in time T(n,m,W) then we can find a matching of weight at least (alpha-epsilon) times the maximum weight of a matching in G in time (epsilon^{-1})^{O(1)}max_{1\le q \le O(epsilon \frac {log {\frac n {epsilon}}} {log epsilon^{-1}})} max_{m_1+...m_q=m} sum_1^qT(min{n,sm_j},m_{j},(epsilon^{-1})^{O(epsilon^{-1})}). In particular, if we combine our result with the recent (1-\epsilon)-approximation algorithm for maximum weight matching in graphs due to Duan and Pettie whose time complexity has a poly-logarithmic dependence on W then we obtain a (1-\epsilon)-approximation algorithm for maximum weight matching in graphs running in time (epsilon^{-1})^{O(1)}(m+n).


All liaisons are dangerous when all your friends are known to us

Abstract: Online Social Networks (OSNs) are used by millions of users worldwide. Academically speaking, there is little doubt about the usefulness of demographic studies conducted on OSNs and, hence, methods to label unknown users from small labeled samples are very useful. However, from the general public point of view, this can be a serious privacy concern. Thus, both topics are tackled in this paper: First, a new algorithm to perform user profiling in social networks is described, and its performance is reported and discussed. Secondly, the experiments --conducted on information usually considered sensitive-- reveal that by just publicizing one's contacts privacy is at risk and, thus, measures to minimize privacy leaks due to social graph data mining are outlined.


Exact Schedulability Test for global-EDF Scheduling of Periodic Hard Real-Time Tasks on Identical Multiprocessors

Abstract: In this paper we consider the scheduling problem of hard real-time systems composed of periodic constrained-deadline tasks upon identical multiprocessor platforms. We assume that tasks are scheduled by using the global-EDF scheduler. We establish an exact schedulability test for this scheduler by exploiting on the one hand its predictability property and by providing on the other hand a feasibility interval so that if it is possible to find a valid schedule for all the jobs contained in this interval, then the whole system will be stamped feasible. In addition, we show by means of a counterexample that the feasibility interval, and thus the schedulability test, proposed by Leung [Leung 1989] is incorrect and we show which arguments are actually incorrect.


Affine-invariant diffusion geometry for the analysis of deformable 3D shapes

Abstract: We introduce an (equi-)affine invariant diffusion geometry by which surfaces that go through squeeze and shear transformations can still be properly analyzed. The definition of an affine invariant metric enables us to construct an invariant Laplacian from which local and global geometric structures are extracted. Applications of the proposed framework demonstrate its power in generalizing and enriching the existing set of tools for shape analysis.


Affine-invariant geodesic geometry of deformable 3D shapes

Abstract: Natural objects can be subject to various transformations yet still preserve properties that we refer to as invariants. Here, we use definitions of affine invariant arclength for surfaces in R^3 in order to extend the set of existing non-rigid shape analysis tools. In fact, we show that by re-defining the surface metric as its equi-affine version, the surface with its modified metric tensor can be treated as a canonical Euclidean object on which most classical Euclidean processing and analysis tools can be applied. The new definition of a metric is used to extend the fast marching method technique for computing geodesic distances on surfaces, where now, the distances are defined with respect to an affine invariant arclength. Applications of the proposed framework demonstrate its invariance, efficiency, and accuracy in shape analysis.


Extending Binary Qualitative Direction Calculi with a Granular Distance Concept: Hidden Feature Attachment

Abstract: In this paper we introduce a method for extending binary qualitative direction calculi with adjustable granularity like OPRAm or the star calculus with a granular distance concept. This method is similar to the concept of extending points with an internal reference direction to get oriented points which are the basic entities in the OPRAm calculus. Even if the spatial objects are from a geometrical point of view infinitesimal small points locally available reference measures are attached. In the case of OPRAm, a reference direction is attached. The same principle works also with local reference distances which are called elevations. The principle of attaching references features to a point is called hidden feature attachment.


Annotated English

Abstract: This document presents Annotated English, a system of diacritical symbols which turns English pronunciation into a precise and unambiguous process. The annotations are defined and located in such a way that the original English text is not altered (not even a letter), thus allowing for a consistent reading and learning of the English language with and without annotations. The annotations are based on a set of general rules that make the frequency of annotations not dramatically high. This makes the reader easily associate annotations with exceptions, and makes it possible to shape, internalise and consolidate some rules for the English language which otherwise are weakened by the enormous amount of exceptions in English pronunciation. The advantages of this annotation system are manifold. Any existing text can be annotated without a significant increase in size. This means that we can get an annotated version of any document or book with the same number of pages and fontsize. Since no letter is affected, the text can be perfectly read by a person who does not know the annotation rules, since annotations can be simply ignored. The annotations are based on a set of rules which can be progressively learned and recognised, even in cases where the reader has no access or time to read the rules. This means that a reader can understand most of the annotations after reading a few pages of Annotated English, and can take advantage from that knowledge for any other annotated document she may read in the future.


Toward Emerging Topic Detection for Business Intelligence: Predictive Analysis of `Meme' Dynamics

Abstract: Detecting and characterizing emerging topics of discussion and consumer trends through analysis of Internet data is of great interest to businesses. This paper considers the problem of monitoring the Web to spot emerging memes - distinctive phrases which act as "tracers" for topics - as a means of early detection of new topics and trends. We present a novel methodology for predicting which memes will propagate widely, appearing in hundreds or thousands of blog posts, and which will not, thereby enabling discovery of significant topics. We begin by identifying measurables which should be predictive of meme success. Interestingly, these metrics are not those traditionally used for such prediction but instead are subtle measures of meme dynamics. These metrics form the basis for learning a classifier which predicts, for a given meme, whether or not it will propagate widely. The utility of the prediction methodology is demonstrated through analysis of memes that emerged online during the second half of 2008.


Exhaustive Verification of Weak Reconstruction For Self Complementary Graphs

Abstract: This paper presents an exhaustive approach for verification of the weak reconstruction of Self Complementary Graphs up to 17 vertices. It describes the general problem of the Reconstruction Conjecture, explaining the complexity involved in checking deck-isomorphism between two graphs. In order to improve the computation time, various pruning techniques have been employed to reduce the number of graph-isomorphism comparisons. These techniques offer great help in proceeding with a reconstructive approach. An analysis of the numbers involved is provided, along with the various limitations of this approach. A list enumerating the number of SC graphs up till 101 vertices is also appended.


Cluster Evaluation of Density Based Subspace Clustering

Abstract: Clustering real world data often faced with curse of dimensionality, where real world data often consist of many dimensions. Multidimensional data clustering evaluation can be done through a density-based approach. Density approaches based on the paradigm introduced by DBSCAN clustering. In this approach, density of each object neighbours with MinPoints will be calculated. Cluster change will occur in accordance with changes in density of each object neighbours. The neighbours of each object typically determined using a distance function, for example the Euclidean distance. In this paper SUBCLU, FIRES and INSCY methods will be applied to clustering 6x1595 dimension synthetic datasets. IO Entropy, F1 Measure, coverage, accurate and time consumption used as evaluation performance parameters. Evaluation results showed SUBCLU method requires considerable time to process subspace clustering; however, its value coverage is better. Meanwhile INSCY method is better for accuracy comparing with two other methods, although consequence time calculation was longer.


Learning a Representation of a Believable Virtual Character's Environment with an Imitation Algorithm

Abstract: In video games, virtual characters' decision systems often use a simplified representation of the world. To increase both their autonomy and believability we want those characters to be able to learn this representation from human players. We propose to use a model called growing neural gas to learn by imitation the topology of the environment. The implementation of the model, the modifications and the parameters we used are detailed. Then, the quality of the learned representations and their evolution during the learning are studied using different measures. Improvements for the growing neural gas to give more information to the character's model are given in the conclusion.


Packet Scheduling in Switches with Target Outflow Profiles

Abstract: The problem of packet scheduling for traffic streams with target outflow profiles traversing input queued switches is formulated in this paper. Target outflow profiles specify the desirable inter-departure times of packets leaving the switch from each traffic stream. The goal of the switch scheduler is to dynamically select service configurations of the switch, so that actual outflow streams ("pulled" through the switch) adhere to their desired target profiles as accurately as possible. Dynamic service controls (schedules) are developed to minimize deviation of actual outflow streams from their targets and suppress stream "distortion". Using appropriately selected subsets of service configurations of the switch, efficient schedules are designed, which deliver high performance at relatively low complexity. Some of these schedules are provably shown to achieve 100% pull-throughput. Moreover, simulations demonstrate that for even substantial contention of streams through the switch, due to stringent/intense target outflow profiles, the proposed schedules achieve closely their target profiles and suppress stream distortion. The switch model investigated here deviates from the classical switching paradigm. In the latter, the goal of packet scheduling is primarily to "push" as much traffic load through the switch as possible, while controlling delay to traverse the switch and keeping congestion/backlogs from exploding. In the model presented here, however, the goal of packet scheduling is to "pull" traffic streams through the switch, maintaining desirable (target) outflow profiles.


Popular b-matchings

Abstract: Suppose that each member of a set of agents has a preference list of a subset of houses, possibly involving ties and each agent and house has their capacity denoting the maximum number of correspondingly agents/houses that can be matched to him/her/it. We want to find a matching $M$, for which there is no other matching $M'$ such that more agents prefer $M'$ to $M$ than $M$ to $M'$. (What it means that an agent prefers one matching to the other is explained in the paper.) Popular matchings have been studied quite extensively, especially in the one-to-one setting. We provide a characterization of popular b-matchings for two defintions of popularity, show some $NP$-hardness results and for certain versions describe polynomial algorithms.


An Algorithm to Reduce the Time Complexity of Earliest Deadline First Scheduling Algorithm in Real-Time System

Abstract: In this paper I have study to Reduce the time Complexity of Earliest Deadline First (EDF), a global scheduling scheme for Earliest Deadline First in Real Time System tasks on a Multiprocessors system. Several admission control algorithms for Earliest Deadline First (EDF) are presented, both for hard and soft real-time tasks. The average performance of these admission control algorithms is compared with the performance of known partitioning schemes. I have applied some modification to the global Earliest Deadline First (EDF) algorithms to decrease the number of task migration and also to add predictability to its behavior. The Aim of this work is to provide a sensitivity analysis for task deadline context of multiprocessor system by using a new approach of EFDF (Earliest Feasible Deadline First) algorithm. In order to decrease the number of migrations we prevent a job from moving one processor to another processor if it is among the m higher priority jobs. Therefore, a job will continue its execution on the same processor if possible (processor affinity). The result of these comparisons outlines some situations where one scheme is preferable over the other. Partitioning schemes are better suited for hard real-time systems, while a global scheme is preferable for soft real-time systems.


PERSEUS Technology: New Trends in Information and Communication Security

Abstract: Using cryptography to protect information and communication has bacically two major drawbacks. First, the specific entropy profile of encrypted data makes their detection very easy. Second, the use of cryptography can be more or less regulated, not to say forbidden, according to the countries. If the right to freely protect our personal and private data is a fundamental right, it must not hinder the action of Nation States with respect to National security. Allowing encryption to citizens holds for bad guys as well. In this paper we propose a new approach in information and communication security that may solve all these issues, thus representing a rather interesting trade-off between apparently opposite security needs. We introduce the concept of scalable security based on computationnally hard problem of coding theory with the PERSEUS technology. The core idea is to encode date with variable punctured convolutional codes in such a way that any cryptanalytic attempt will require a time-consuming encoder reconstruction in order to decode. By adding noise in a suitable way, that reconstruction becomes untractable in practice except for Intelligence services that however must use supercomputers during a significant, scalable amount of time. Hence it limits naturally any will to unduly performs such attacks (eg. against citizens' privacy). On the users' side, encoder and noise parameters are first exchanged through an initial, short HTTPS session. The principles behind that approach have been mathematically validated in 1997 and 2007. We present the PERSEUS library we have developed under the triple GPL/LGPL/MPL licences. This library can be used to protect any kind of data.


A Searchable Compressed Edit-Sensitive Parsing

Abstract: Practical data structures for the edit-sensitive parsing (ESP) are proposed. Given a string S, its ESP tree is equivalent to a context-free grammar G generating just S, which is represented by a DAG. Using the succinct data structures for trees and permutations, G is decomposed to two LOUDS bit strings and single array in (1+\epsilon)n\log n+4n+o(n) bits for any 0<\epsilon <1 and the number n of variables in G. The time to count occurrences of P in S is in O(\frac{1}{\epsilon}(m\log n+occ_c(\log m\log u)), whereas m = |P|, u = |S|, and occ_c is the number of occurrences of a maximal common subtree in ESPs of P and S. The efficiency of the proposed index is evaluated by the experiments conducted on several benchmarks complying with the other compressed indexes.


Abstract: The purpose of this paper is to develop further the main concepts of Phenomena Dynamic Logic (P-DL) and Cognitive Dynamic Logic (C-DL), presented in the previous paper. The specific character of these logics is in matching vagueness or fuzziness of similarity measures to the uncertainty of models. These logics are based on the following fundamental notions: generality relation, uncertainty relation, simplicity relation, similarity maximization problem with empirical content and enhancement (learning) operator. We develop these notions in terms of logic and probability and developed a Probabilistic Dynamic Logic of Phenomena and Cognition (P-DL-PC) that relates to the scope of probabilistic models of brain. In our research the effectiveness of suggested formalization is demonstrated by approximation of the expert model of breast cancer diagnostic decisions. The P-DL-PC logic was previously successfully applied to solving many practical tasks and also for modelling of some cognitive processes.


Parallel sparse matrix-vector multiplication as a test case for hybrid MPI+OpenMP programming

Abstract: We evaluate optimized parallel sparse matrix-vector operations for two representative application areas on widespread multicore-based cluster configurations. First the single-socket baseline performance is analyzed and modeled with respect to basic architectural properties of standard multicore chips. Going beyond the single node, parallel sparse matrix-vector operations often suffer from an unfavorable communication to computation ratio. Starting from the observation that nonblocking MPI is not able to hide communication cost using standard MPI implementations, we demonstrate that explicit overlap of communication and computation can be achieved by using a dedicated communication thread, which may run on a virtual core. We compare our approach to pure MPI and the widely used "vector-like" hybrid programming strategy.


Optimizing ccNUMA locality for task-parallel execution under OpenMP and TBB on multicore-based systems

Abstract: Task parallelism as employed by the OpenMP task construct or some Intel Threading Building Blocks (TBB) components, although ideal for tackling irregular problems or typical producer/consumer schemes, bears some potential for performance bottlenecks if locality of data access is important, which is typically the case for memory-bound code on ccNUMA systems. We present a thin software layer ameliorates adverse effects of dynamic task distribution by sorting tasks into locality queues, each of which is preferably processed by threads that belong to the same locality domain. Dynamic scheduling is fully preserved inside each domain, and is preferred over possible load imbalance even if nonlocal access is required, making this strategy well-suited for typical multicore-mutisocket systems. The effectiveness of the approach is demonstrated by using a blocked six-point stencil solver as a toy model.


Design of Transport Layer Based Hybrid Covert Channel Detection Engine

Abstract: Computer network is unpredictable due to information warfare and is prone to various attacks. Such attacks on network compromise the most important attribute, the privacy. Most of such attacks are devised using special communication channel called "Covert Channel". The word "Covert" stands for hidden or non-transparent. Network Covert Channel is a concealed communication path within legitimate network communication that clearly violates security policies laid down. The non-transparency in covert channel is also referred to as trapdoor. A trapdoor is unintended design within legitimate communication whose motto is to leak information. Subliminal channel, a variant of covert channel works similarly except that the trapdoor is set in a cryptographic algorithm. A composition of covert channel with subliminal channel is the "Hybrid Covert Channel". Hybrid covert channel is homogenous or heterogeneous mixture of two or more variants of covert channels either active at same instance or at different instances of time. Detecting such malicious channel activity plays a vital role in removing threat to the legitimate network. In this paper, we present a study of multi-trapdoor covert channels and introduce design of a new detection engine for hybrid covert channel in transport layer visualized in TCP and SSL.


Integration of Communication Analysis and the OO Method: Manual derivation of the Conceptual Model. The SuperStationery Co. lab demo

Abstract: This document presents a lab demo that exemplifies the manual derivation of an OO Method conceptual model, taking as input a Communication Analysis requirements model. In addition, it is described how the conceptual model is created in the OLIVANOVA Modeler tool. The lab demo corresponds to part of the business processes of a fictional small and medium enterprise named SuperStationery Co. This company provides stationery and office material to its clients. The company acts as a as intermediary: the company has a catalogue of products that are bought from suppliers and sold to clients. This lab demo, besides illustrating the derivation technique, demonstrates that the technique is feasible in practice. Also, the results of this lab demo provide a valuable feedback in order to improve the derivation technique.


The degree structure of Weihrauch-reducibility

Abstract: We answer a question by Vasco Brattka and Guido Gherardi by proving that the Weihrauch-lattice is not a Brouwer algebra. The computable Weihrauch-lattice is also not a Heyting algebra, but the continuous Weihrauch-lattice is. We further investigate the existence of infinite infima and suprema, as well as embeddings of the Medvedev-degrees into the Weihrauch-degrees.