Towards scaling up DynAlloy analysis using predicate abstraction

DynAlloy is an extension to the Alloy specifi cation language suitable for modeling properties of executions of software systems. DynAlloy provides fully automated support for verifying properties of programs, in the style of the Alloy Analyzer, i.e., by exhaustively searching for counterexamples of properties in bounded scenarios (bounded domains and iterations of programs). But, as for other automated analysis techniques, the so called state explotion problem makes the analysis feasible only for small bounds. In this paper, we take advantage of an abstraction technique known as predicate abstraction, for scaling up the analysis of DynAlloy specifi cations. The implementation of predicate abstraction we present enables us to substantially increase the domain and iteration bounds in some case studies, and its use is fully automated. Our implementation is relatively e cient, exploiting the reuse of already calculated abstractions when these are available, and an "on the fly" check of traces when looking for counterexamples. We introduce the implementation of the technique, and some preliminary experimental results with case studies, to illustrate the benefi ts of the technique.VI Workshop Ingeniería de Software (WIS)Red de Universidades con Carreras en Informática (RedUNCI

Towards scaling up DynAlloy analysis using predicate abstraction

DynAlloy is an extension to the Alloy specifi cation language suitable for modeling properties of executions of software systems. DynAlloy provides fully automated support for verifying properties of programs, in the style of the Alloy Analyzer, i.e., by exhaustively searching for counterexamples of properties in bounded scenarios (bounded domains and iterations of programs). But, as for other automated analysis techniques, the so called state explotion problem makes the analysis feasible only for small bounds. In this paper, we take advantage of an abstraction technique known as predicate abstraction, for scaling up the analysis of DynAlloy specifi cations. The implementation of predicate abstraction we present enables us to substantially increase the domain and iteration bounds in some case studies, and its use is fully automated. Our implementation is relatively e cient, exploiting the reuse of already calculated abstractions when these are available, and an "on the fly" check of traces when looking for counterexamples. We introduce the implementation of the technique, and some preliminary experimental results with case studies, to illustrate the benefi ts of the technique.VI Workshop Ingeniería de Software (WIS)Red de Universidades con Carreras en Informática (RedUNCI

Object replication in a distributed system

PhD ThesisA number of techniques have been proposed for the construction of fault—tolerant applications. One of these techniques is to replicate vital system resources so that if one copy fails sufficient copies may still remain operational to allow the application to continue to function. Interactions with replicated resources are inherently more complex than non—replicated interactions, and hence some form of replication transparency is necessary. This may be achieved by employing replica consistency protocols to mask replica failures and maintain consistency of state between functioning replicas. To achieve consistency between replicas it is necessary to ensure that all replicas receive the same set of messages in the same order, despite failures at the senders and receivers. This can be accomplished by making use of order preserving reliable communication protocols. However, we shall show how it can be more efficient to use unordered reliable communication and to impose ordering at the application level, by making use of syntactic knowledge of the application. This thesis develops techniques for replicating objects: in general this is harder than replicating data, as objects (which can contain data) can contain calls on other objects. Handling replicated objects is essentially the same as handling replicated computations, and presents more problems than simply replicating data. We shall use the concept of the object to provide transparent replication to users: a user will interact with only a single object interface which hides the fact that the object is actually replicated. The main aspects of the replication scheme presented in this thesis have been fully implemented and tested. This includes the design and implementation of a replicated object invocation protocol and the algorithms which ensure that (replicated) atomic actions can manipulate replicated objects.Research Studentship, Science and Engineering Research Council. Esprit Project 2267 (Integrated Systems Architecture)

Computer Science and Technology Series : XV Argentine Congress of Computer Science. Selected papers

CACIC'09 was the fifteenth Congress in the CACIC series. It was organized by the School of Engineering of the National University of Jujuy. The Congress included 9 Workshops with 130 accepted papers, 1 main Conference, 4 invited tutorials, different meetings related with Computer Science Education (Professors, PhD students, Curricula) and an International School with 5 courses. CACIC 2009 was organized following the traditional Congress format, with 9 Workshops covering a diversity of dimensions of Computer Science Research. Each topic was supervised by a committee of three chairs of different Universities. The call for papers attracted a total of 267 submissions. An average of 2.7 review reports were collected for each paper, for a grand total of 720 review reports that involved about 300 different reviewers. A total of 130 full papers were accepted and 20 of them were selected for this book.Red de Universidades con Carreras en Informática (RedUNCI

A belief-desire-intention architechture with a logic-based planner for agents in stochastic domains

This dissertation investigates high-level decision making for agents that are both goal and utility driven. We develop a partially observable Markov decision process (POMDP) planner which is an extension of an agent programming language called DTGolog, itself an extension of the Golog language. Golog is based on a logic for reasoning about action—the situation calculus. A POMDP planner on its own cannot cope well with dynamically changing environments and complicated goals. This is exactly a strength of the belief-desire-intention (BDI) model: BDI theory has been developed to design agents that can select goals intelligently, dynamically abandon and adopt new goals, and yet commit to intentions for achieving goals. The contribution of this research is twofold: (1) developing a relational POMDP planner for cognitive robotics, (2) specifying a preliminary BDI architecture that can deal with stochasticity in action and perception, by employing the planner.ComputingM. Sc. (Computer Science

Computer Science and Technology Series : XV Argentine Congress of Computer Science. Selected papers

CACIC'09 was the fifteenth Congress in the CACIC series. It was organized by the School of Engineering of the National University of Jujuy. The Congress included 9 Workshops with 130 accepted papers, 1 main Conference, 4 invited tutorials, different meetings related with Computer Science Education (Professors, PhD students, Curricula) and an International School with 5 courses. CACIC 2009 was organized following the traditional Congress format, with 9 Workshops covering a diversity of dimensions of Computer Science Research. Each topic was supervised by a committee of three chairs of different Universities. The call for papers attracted a total of 267 submissions. An average of 2.7 review reports were collected for each paper, for a grand total of 720 review reports that involved about 300 different reviewers. A total of 130 full papers were accepted and 20 of them were selected for this book.Red de Universidades con Carreras en Informática (RedUNCI