25 research outputs found
Counterfactual Causality from First Principles?
In this position paper we discuss three main shortcomings of existing
approaches to counterfactual causality from the computer science perspective,
and sketch lines of work to try and overcome these issues: (1) causality
definitions should be driven by a set of precisely specified requirements
rather than specific examples; (2) causality frameworks should support system
dynamics; (3) causality analysis should have a well-understood behavior in
presence of abstraction.Comment: In Proceedings CREST 2017, arXiv:1710.0277
GSOS for non-deterministic processes with quantitative aspects
Recently, some general frameworks have been proposed as unifying theories for
processes combining non-determinism with quantitative aspects (such as
probabilistic or stochastically timed executions), aiming to provide general
results and tools. This paper provides two contributions in this respect.
First, we present a general GSOS specification format (and a corresponding
notion of bisimulation) for non-deterministic processes with quantitative
aspects. These specifications define labelled transition systems according to
the ULTraS model, an extension of the usual LTSs where the transition relation
associates any source state and transition label with state reachability weight
functions (like, e.g., probability distributions). This format, hence called
Weight Function SOS (WFSOS), covers many known systems and their bisimulations
(e.g. PEPA, TIPP, PCSP) and GSOS formats (e.g. GSOS, Weighted GSOS,
Segala-GSOS, among others).
The second contribution is a characterization of these systems as coalgebras
of a class of functors, parametric on the weight structure. This result allows
us to prove soundness of the WFSOS specification format, and that
bisimilarities induced by these specifications are always congruences.Comment: In Proceedings QAPL 2014, arXiv:1406.156
Structural operational semantics for non-deterministic processes with quantitative aspects
General frameworks have been recently proposed as unifying theories for
processes combining non-determinism with quantitative aspects (such as
probabilistic or stochastically timed executions), aiming to provide general
results and tools. This paper provides two contributions in this respect.
First, we present a general GSOS specification format and a corresponding
notion of bisimulation for non-deterministic processes with quantitative
aspects. These specifications define labelled transition systems according to
the ULTraS model, an extension of the usual LTSs where the transition relation
associates any source state and transition label with state reachability weight
functions (like, e.g., probability distributions). This format, hence called
Weight Function GSOS (WF-GSOS), covers many known systems and their
bisimulations (e.g. PEPA, TIPP, PCSP) and GSOS formats (e.g. GSOS, Weighted
GSOS, Segala-GSOS, among others).
The second contribution is a characterization of these systems as coalgebras
of a class of functors, parametric on the weight structure. This result allows
us to prove soundness and completeness of the WF-GSOS specification format, and
that bisimilarities induced by these specifications are always congruences.Comment: Extended version of arXiv:1406.206
An introduction to (Co)algebras and (Co)induction and their application to the semantics of programming languages
This report summarizes operational approaches to the formal
semantics of programming languages and shows that they can be
interpreted inductively by least fixed points as well as
coinductively by greatest fixed points. While the inductive
interpretation gives semantics to all terminating programs,
the coinductive one defines moreover also a semantics for all
non-terminating programs. This is especially important in
areas where programs do not terminate in general, e.g. data
bases, operating systems, or control software in embedded
systems. The semantic foundations described in this report can
be used to verify that transformations (e.g. in compilers) of
such software systems are correct.
In the course of this report, coalgebras and coinduction are
introduced, starting with a gentle intuitive motivation and
ending with a detailed mathematical description within the
notions of category theory
Extended static checking by calculation using the pointfree transform
The pointfree transform offers to the predicate calculus what the La- place transform offers to the differential/integral calculus: the possibility of chang- ing the underlying mathematical space so as to enable agile algebraic calculation. This paper addresses the foundations of the transform and its application to a calculational approach to extended static checking (ESC) in the context of ab- stract modeling. In particular, a calculus is given whose rules help in breaking the complexity of the proof obligations involved in static checking arguments. The close connection between such calculus and that of weakest pre-conditions makes it possible to use the latter in ESC proof obligation discharge, where point- free notation is again used, this time to calculate with invariant properties to be maintained.
A connection with the “everything is a relation” lemma of Alloy is estab- lished, showing how close to each other the pointfree and Alloy notations are. The main advantage of this connection is that of complementing pen-and-paper pointfree calculations with model checking support wherever validating sizable abstract models.Fundação para a Ciência e a Tecnologia (FCT
Computer Aided Verification
This open access two-volume set LNCS 13371 and 13372 constitutes the refereed proceedings of the 34rd International Conference on Computer Aided Verification, CAV 2022, which was held in Haifa, Israel, in August 2022. The 40 full papers presented together with 9 tool papers and 2 case studies were carefully reviewed and selected from 209 submissions. The papers were organized in the following topical sections: Part I: Invited papers; formal methods for probabilistic programs; formal methods for neural networks; software Verification and model checking; hyperproperties and security; formal methods for hardware, cyber-physical, and hybrid systems. Part II: Probabilistic techniques; automata and logic; deductive verification and decision procedures; machine learning; synthesis and concurrency. This is an open access book
Foundations of Software Science and Computation Structures
This open access book constitutes the proceedings of the 22nd International Conference on Foundations of Software Science and Computational Structures, FOSSACS 2019, which took place in Prague, Czech Republic, in April 2019, held as part of the European Joint Conference on Theory and Practice of Software, ETAPS 2019. The 29 papers presented in this volume were carefully reviewed and selected from 85 submissions. They deal with foundational research with a clear significance for software science