Kima - an Automated Error Correction System for Concurrent Logic Programs.

In this paper a formal model for program dependence analysis of concurrent logic programs is proposed with the following contributions. First, two languageindependent program representations are presented for explicitly representing control flows and/or data flows in a concurrent logic program. Then based on these representations, program dependences between literals in concurrent logic programs are defined formally, and a dependence-based program representation named the Literal Dependence Net (LDN) is presented for explicitly representing primary program dependences in a concurrent logic program. Finally, as applications of the LDNs, some important software engineering activities including program slicing, debugging, testing, complexity measurement, and maintenance are discussed in a programming environment for concurrent logic programs. 1 Introduction It is well-known that programming environments are very important for the acceptance of programming languages. Unfortunately, rece...

OASIS is a formal approach for the specification of object oriented conceptual models. In OASIS conceptual schemas of information systems are represented as societies of interacting concurrent objects. Animating such models in order to validate the specification of information systems is a topic of interest in requirements engineering. Thus a basic execution model for OASIS specifications has been developed. Concurrent Logic Programming is a suitable paradigm for distributed computation allowing a natural representation of concurrence. Using Concurrent Logic Programming, OASIS specifications are animated according to OASIS execution model. In this work, we show how OASIS concepts are directly mapped into concurrent logic programming concepts. To illustrate our ideas, an example of a bank account codified in KL1 is given and parts of the program that animates its corresponding OASIS specification are shown. This work has been developed in the context of a CASE tool supporting the OASIS approach. Our aim is to build a module for animation and validation of specifications. A preliminary version of this module is presented.

A problem which confronts the developers of concurrent logic programming (CLP) systems concerns the design of the programming environment, particularly the provision of debugging tools. Debugging tools are useful for many activities besides identifying bugs: they can help in program testing and demonstration, in software experiments, and in teaching the language semantics. For CLP languages the questions of what debugging tools should be provided, and of how they should be used, are still open. Although the languages are closely related to other logic programming and concurrent programming languages, they are sufficiently different that new debugging techniques are required. This paper describes a primarily channel-oriented debugging methodology and a set of debugging tools that we have developed in the light of our experience in using and teaching the CLP language Parlog. With these tools a programmer can test a program by observing communication on channels, opening up a process to examine the activity on internal channels and, if necessary, to check in detail the execution steps of a process. Almost all of the ideas, which are equally applicable to other CLP languages, have been implemented in two commercial Parlog systems. As well as fulfilling the needs of existing users of CLP languages, we believe that the tools emphasise the attractions of CLP as a concurrent programming paradigm, since they are made possible by the unique attributes of CLP.

This paper explores the use of rough set theory for feature selection in high dimensional haptic-based handwritten signatures (exploited for user identification). Two rough set-based methods for feature selection are analyzed, the first is a greedy approach while the second relies on genetic algorithms to find minimal subsets of attributes. Also, to further reduce the haptic feature space while maximizing user identification accuracy, a method is proposed where feature vectors are subsampled prior to the feature selection procedure. Rough set-generated minimal subsets are initially exploited to determine the importance of different haptic data types (e.g. force, position, torque and orientation) in discriminating between different users. In addition, a comparison between rough set-based methods and classical machine learning techniques in the selection of minimal information-preserving subsets of features in high dimensional haptic datasets, is provided. The criteria for comparison are the length of the selected subsets of features and their corresponding discrimination power. Support Vector Machine classifiers are used to evaluate the accuracy of the selected minimal feature vectors. The results demonstrated that the combination of rough set and genetic algorithm techniques can outperform well-established machine learning methods in the selection of minimal subsets of features present in haptic-based handwritten signatures.

Saraswat recently introduced the framework of concurrent constraint programming [14]. The essence of the framework is that computations consist of concurrent agents interacting by communicating constraints. Several concurrent constraint programming languages have been defined. They differ in the kinds of constraints that can be used as well as the kinds of operations on constraints which are available. In this paper we introduce a very simple concurrent constraint language we call Lucy, designed to closely mimic the actor model of computation. Agents can communicate only by the posting of constraints upon bags (un-ordered collections possibly with duplicate elements). This very impoverished concurrent constraint language is a syntactic subset of Janus, a concurrent constraint language which closely resembles concurrent logic programming languages such as Guarded Horn Clauses [21], Strand [5], Parlog [2] and Flat Concurrent Prolog [13]. By identifying the subset of Janus which is an actor language, we elucidate the relationship between actors and concurrent logic programming (and its generalization as concurrent constraint programming). Lucy is best not thought of as a unification of logic and constraint programming with actor and object-oriented programming, but as the missing link between these programming language genera.

As large amounts of garbage are generated in concurrent logic programs, it becomes necessary to salvage used memory frequently and efficiently, with a garbage collector. Another approach is to detect when a data structure becomes garbage and reuse it. In concurrent languages it is particularly difficult to determine when a data structure is garbage and suitable for destructive update. Dynamic schemes, such as reference counting, incur space and time overheads that can be unacceptable. In contrast, static-analysis techniques identify data objects whose storage may be reused. Information from static analysis can be used by the compiler in generating appropriate instructions for reuse, incurring little or no runtime overhead. In this paper we present a new static-analysis technique for reuse detection. We present empirical performance measurements comparing the new scheme against binary reference counting (MRB). It is shown that, a simple static analysis can achieve most of the benefits of MRB and improve the execution time.

The use of types to deal with access capabilities of program entities is becoming increasingly popular.In concurrent logic programming, the first attempt was made in Moded Flat GHC in 1990, which gave polarity structures (modes) to every variable occurrence and every predicate argument. Strong moding turned out to play fundamental rôles in programming, implementation and the in-depthunderstanding of constraint-based concurrent computation.The moding principle guarantees that each variable is written only once and encourages capability-conscious programming. Furthermore, it gives less generic modes to programs that discard or duplicate data, thus providing the view of “data as resources.” A simple linearity system built upon the mode system distinguishes variables read only once from those read possibly many times, enabling compile-time garbage collection. Compared to linear types studied in other programming paradigms, the primary issue in constraint-based concurrency has been to deal with logical variables and highly non-strict data structures they induce.In this paper, we put our resource-consciousness one step forward and consider a class of ‘ecological’ programs which recycle or return all the resources given to them while allowing concurrent reading of data structures via controlled aliasing. This completely recyclic subset enforces us to think more about resources, but the resulting programs enjoy high symmetry which we believe has more than aesthetic implications to our programming practice in general.The type system supporting recyclic concurrent programming gives a [−1, +1] capability to each occurrence of variable and function symbols (constructors), where positive/negative values mean read/write capabilities, respectively, and fractions mean non-exclusive read/write paths. The capabilities are intended to be statically checked or reconstructed so that one can tell the polarity and exclusiveness of each piece of information handled by concurrent processes. The capability type system refines and integrates the mode system and the linearity system for Moded Flat GHC. Its arithmetic formulation contributes to the simplicity.The execution of a recyclic program proceeds so that every variable has zero-sum capability and the resources (i.e., constructors weighted by their capabilities) a process absorbs match the resources it emits. Constructors accessed by a process withan exclusive read capability can be reused for other purposes.The first half of this paper is devoted to a tutorial introduction to constraint-based concurrency in the hope that it will encourage crossfertilization of different concurrency formalisms.KeywordsLogic ProgramMode GraphLogical VariableMode ConstraintProgram ClauseThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

A methodology for developing sound proof systems for program verification is demonstrated by the development of a proof system for reasoning about concurrent programs based on the unity logic of K.M. Chandy and J. Misra (1988). This proof system has been validated by an automated theorem prover, a computer program that checks the correctness of proofs. The Boyer-Moore logic in which the proof system is formalized and the Boyer-Moore theorem prover which mechanizes this logic are described. The motivation behind the unity logic and the way in which it may be used to prove the correctness of concurrent programs are examined. A proof system for concurrent programs based on the unity logic system is provided as an example. An operational semantics of concurrency is formalized in Boyer-Moore logic by use of the transition system model. Unity's proof rules are proved as theorems about this operational semantics. The proofs of these theorems are mechanically checked. The entire proof system has been verified by the Boyer-Moore prover, making it possible to prove mechanically the consequence of other concurrent programs.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Variable and value ordering heuristics for the job shop scheduling constraint satisfaction problem

This collection of original research provides a comprehensive survey of developments at the leading edge of concurrent object-oriented programming. It documents progress—from general concepts to specific descriptions—in programming language design, semantic tools, systems, architectures, and applications. Chapters are written at a tutorial level and are accessible to a wide audience, including researchers, programmers, and technical managers. The problem of designing systems for concurrent programming has become an increasingly important area of research in computer science with a concomitant increase in the popularity of object-based programming. Because parallelism is a natural consequence of the use of objects, the development of systems for concurrent object-oriented programming is providing important software support for a new generation of concurrent computers.

A wide variety of problems, ranging from planning and scheduling tasks in industry to making autonomous decisions in smart environments, can be modelled as constraint satisfaction problems (CSPs). While this general mathematical framework facilitates the reuse of algorithms for many different types of problems, the fact that CSPs are NP-complete gives them an exponential worst-case computational complexity. This complexity imposes severe restrictions on the size of the problem, as virtually all applications require problems to be solved in a timely fashion. However, despite being NP-complete problems, CSPs can often be solved efficiently in practice, making this worst-case complexity largely uninformative. The structure of a problem and of the search space have been used to identify classes of tractable problems and design more efficient solving techniques with better theoretical guarantees. Unfortunately, the worst-case bounds of these algorithms are hardly more informative when it comes to their practical efficiency, and exploiting this structure is challenging because efficient algorithms do not exist for many related tasks. This dissertation studies the structure of problems and their search space and how these influence the search times of algorithms. It provides additional insights into the computational complexity and practical efficiency of search algorithms, which can, for instance, be used to select the best algorithm for a given problem and aid in the design of more efficient solving techniques. This work also contributes towards improving the solving efficiency more directly by proposing improved ways to exploit the structure of a problem and the search space algorithmically.

Quantified Constraint Satisfaction Problems (QCSP) are a generalization of Constraint Satisfaction Problems (CSP) in which variables may be quantified existentially and universally. QCSP offers a natural framework to express PSPACE problems as finite two-player games or planning under uncertainty. State-of-the-art QCSP solvers have an important drawback: they explore much larger combinatorial spaces than the natural search space of the original problem since they are unable to recognize that some sub-problems are necessarily true. We introduce a new tool, inspired by the cut rule of Prolog as a tool under responsibility of the designer of the QCSP, to prune those parts of the search space which are by construction known to be useless. We use this new tool to restore on one hand the annihilator property of true for disjunction in QCSP solver and, on the other hand, to prune the search space in two-player games. It is a simple solution to use efficiently QCSP to design finite two-player games without restricting the QCSP language. This tool does not need to modify the QCSP solver but has only one requirement: be able to tell the QCSP solver that the current QCSP is solved. Our QCSP solver built over Ge Code, a CSP library, obtained very good results compared to state-of-the-art QCSP solvers.

Handbook of Constraint Programming

Given the preferences of several agents over a set of alternatives, there may be competing views on which of the alternative would be “best” to choose. We propose a formal model, grounded in social choice theory, for providing a justification for a given choice in the context of a given corpus of basic normative principles (so-called axioms) on which to base any possible step-by-step explanation for why a given target alternative should be elected in a given situation. Thus, our notion of justification has both an explanatory and a normative component. We also develop an algorithm for computing such justifications that exploits the analogy between the notion of explanation and the concept of minimal unsatisfiable subset used in constraint programming. Finally, we report on an application of a proof-of-concept implementation of our approach for an experimental study of the explanatory power of several axioms proposed in the social choice literature.

A new direct spectrometric micromethod for the determination of the available bilirubin binding sites of serum (S-ABBS) using bromphenol blue has been applied to 298 blood specimens collected from infants immediately before starting the first exchange transfusion. A relative number fraction of 0.07 of the material, characterized by having the lowest S-ABBS values, includes seven of the nine cases (i.e. a relative number fraction of 0.78) with autoptically verified kernicterus (KI). The two infants with KI but higher S-ABBS values differed in having severe neurological symptoms before the examination. The mean substance concentration of bilirubin in these nine sera was 288 mumol/l. The correlation of KI to the body mass at birth, to the substance concentration of serum albumin, and to the substance concentration of serum bilirubin is given, and the sources of error concerning the method are discussed. The present method is proposed for determining a type of quantity that is important, among other types of data, in deciding on the need for exchange transfusion in icteric (premature) newborns.