43 research outputs found
A Backward Analysis for Constraint Logic Programs
One recurring problem in program development is that of understanding how to
re-use code developed by a third party. In the context of (constraint) logic
programming, part of this problem reduces to figuring out how to query a
program. If the logic program does not come with any documentation, then the
programmer is forced to either experiment with queries in an ad hoc fashion or
trace the control-flow of the program (backward) to infer the modes in which a
predicate must be called so as to avoid an instantiation error. This paper
presents an abstract interpretation scheme that automates the latter technique.
The analysis presented in this paper can infer moding properties which if
satisfied by the initial query, come with the guarantee that the program and
query can never generate any moding or instantiation errors. Other applications
of the analysis are discussed. The paper explains how abstract domains with
certain computational properties (they condense) can be used to trace
control-flow backward (right-to-left) to infer useful properties of initial
queries. A correctness argument is presented and an implementation is reported.Comment: 32 page
Semantics for possibilistic answer set programs: uncertain rules versus rules with uncertain conclusions
Although Answer Set Programming (ASP) is a powerful framework for declarative problem solving, it cannot in an intuitive way handle situations in which some rules are uncertain, or in which it is more important to satisfy some constraints than others. Possibilistic ASP (PASP) is a natural extension of ASP in which certainty weights are associated with each rule. In this paper we contrast two different views on interpreting the weights attached to rules. Under the first view, weights reflect the certainty with which we can conclude the head of a rule when its body is satisfied. Under the second view, weights reflect the certainty that a given rule restricts the considered epistemic states of an agent in a valid way, i.e. it is the certainty that the rule itself is correct. The first view gives rise to a set of weighted answer sets, whereas the second view gives rise to a weighted set of classical answer sets
A Brief History of Updates of Answer-Set Programs
Funding Information: The authors would like to thank JosĂ© Alferes, Martin Baláz, Federico Banti, Antonio Brogi, Martin Homola, LuĂs Moniz Pereira, Halina Przymusinska, Teodor C. Przymusinski, and Theresa Swift, with whom they worked on the topic of this paper over the years, as well as Ricardo Gonçalves and Matthias Knorr for valuable comments on an earlier draft of this paper. The authors would also like to thank the anonymous reviewers for their insightful comments and suggestions, which greatly helped us improve this paper. The authors were partially supported by Fundação para a CiĂŞncia e Tecnologia through projects FORGET (PTDC/CCI-INF/32219/2017) and RIVER (PTDC/CCI-COM/30952/2017), and strategic project NOVA LINCS (UIDB/04516/2020). Publisher Copyright: © The Author(s), 2022. Published by Cambridge University Press.Over the last couple of decades, there has been a considerable effort devoted to the problem of updating logic programs under the stable model semantics (a.k.a. answer-set programs) or, in other words, the problem of characterising the result of bringing up-to-date a logic program when the world it describes changes. Whereas the state-of-the-art approaches are guided by the same basic intuitions and aspirations as belief updates in the context of classical logic, they build upon fundamentally different principles and methods, which have prevented a unifying framework that could embrace both belief and rule updates. In this paper, we will overview some of the main approaches and results related to answer-set programming updates, while pointing out some of the main challenges that research in this topic has faced.publishersversionpublishe
Weighted logics for artificial intelligence : an introductory discussion
International audienceBefore presenting the contents of the special issue, we propose a structured introductory overview of a landscape of the weighted logics (in a general sense) that can be found in the Artificial Intelligence literature, highlighting their fundamental differences and their application areas
Bunched logics: a uniform approach
Bunched logics have found themselves to be key tools in modern computer science, in particular through the industrial-level program verification formalism Separation Logic. Despite this—and in contrast to adjacent families of logics like modal and substructural logic—there is a lack of uniform methodology in their study, leaving many evident variants uninvestigated and many open problems unresolved. In this thesis we investigate the family of bunched logics—including previously unexplored intuitionistic variants—through two uniform frameworks. The first is a system of duality theorems that relate the algebraic and Kripke-style interpretations of the logics; the second, a modular framework of tableaux calculi that are sound and complete for both the core logics themselves, as well as many classes of bunched logic model important for applications in program verification and systems modelling. In doing so we are able to resolve a number of open problems in the literature, including soundness and completeness theorems for intuitionistic variants of bunched logics, classes of Separation Logic models and layered graph models; decidability of layered graph logics; a characterisation theorem for the classes of bunched logic model definable by bunched logic formulae; and the failure of Craig interpolation for principal bunched logics. We also extend our duality theorems to the categorical structures suitable for interpreting predicate versions of the logics, in particular hyperdoctrinal structures used frequently in Separation Logic
19th Brazilian Logic Conference: Book of Abstracts
This is the book of abstracts of the 19th Brazilian Logic Conferences. The Brazilian Logic Conferences (EBL) is one of the most traditional logic conferences in South America. Organized by the Brazilian Logic Society (SBL), its main goal is to promote the dissemination of research in logic in a broad sense. It has been occurring since 1979, congregating logicians of different fields — mostly philosophy, mathematics and computer science — and with different backgrounds — from undergraduate students to senior researchers. The meeting is an important moment for the Brazilian and South American logical community to join together and discuss recent developments of the field. The areas of logic covered in the conference spread over foundations and philosophy of science, analytic philosophy, philosophy and history of logic, mathematics, computer science, informatics, linguistics and artificial intelligence. Previous editions of the EBL have been a great success, attracting researchers from all over Latin America and elsewhere.
The 19th edition of EBL takes place from May 6-10, 2019, in the beautiful city of JoĂŁo Pessoa, at the northeast coast of Brazil. It is conjointly organized by Federal University of ParaĂba (UFPB), whose main campus is located in JoĂŁo Pessoa, Federal University of Campina Grande (UFCG), whose main campus is located in the nearby city of Campina Grande (the second-largest city in ParaĂba state) and SBL. It is sponsored by UFPB, UFCG, the Brazilian Council for Scientific and Technological Development (CNPq) and the State Ministry of Education, Science and Technology of ParaĂba. It takes place at Hotel Luxxor Nord TambaĂş, privileged located right in front TambaĂş beach, one of JoĂŁo Pessoa’s most famous beaches
Affine Disjunctive Invariant Generation with Farkas' Lemma
Invariant generation is the classical problem that aims at automated
generation of assertions that over-approximates the set of reachable program
states in a program. We consider the problem of generating affine invariants
over affine while loops (i.e., loops with affine loop guards, conditional
branches and assignment statements), and explore the automated generation of
disjunctive affine invariants. Disjunctive invariants are an important class of
invariants that capture disjunctive features in programs such as multiple
phases, transitions between different modes, etc., and are typically more
precise than conjunctive invariants over programs with these features. To
generate tight affine invariants, existing constraint-solving approaches have
investigated the application of Farkas' Lemma to conjunctive affine invariant
generation, but none of them considers disjunctive affine invariants