100 research outputs found
Verification of Imperative Programs by Constraint Logic Program Transformation
We present a method for verifying partial correctness properties of
imperative programs that manipulate integers and arrays by using techniques
based on the transformation of constraint logic programs (CLP). We use CLP as a
metalanguage for representing imperative programs, their executions, and their
properties. First, we encode the correctness of an imperative program, say
prog, as the negation of a predicate 'incorrect' defined by a CLP program T. By
construction, 'incorrect' holds in the least model of T if and only if the
execution of prog from an initial configuration eventually halts in an error
configuration. Then, we apply to program T a sequence of transformations that
preserve its least model semantics. These transformations are based on
well-known transformation rules, such as unfolding and folding, guided by
suitable transformation strategies, such as specialization and generalization.
The objective of the transformations is to derive a new CLP program TransfT
where the predicate 'incorrect' is defined either by (i) the fact 'incorrect.'
(and in this case prog is not correct), or by (ii) the empty set of clauses
(and in this case prog is correct). In the case where we derive a CLP program
such that neither (i) nor (ii) holds, we iterate the transformation. Since the
problem is undecidable, this process may not terminate. We show through
examples that our method can be applied in a rather systematic way, and is
amenable to automation by transferring to the field of program verification
many techniques developed in the field of program transformation.Comment: In Proceedings Festschrift for Dave Schmidt, arXiv:1309.455
A unified view of parameterized verification of abstract models of broadcast communication
We give a unified view of different parameterized models of concurrent and distributed systems with broadcast communication based on transition systems. Based on the resulting formal models, we discuss related verification methods and tools based on abstractions and symbolic state exploration
Parameterized verification
The goal of parameterized verification is to prove the correctness of a system specification regardless of the number of its components. The problem is of interest in several different areas: verification of hardware design, multithreaded programs, distributed systems, and communication protocols. The problem is undecidable in general. Solutions for restricted classes of systems and properties have been studied in areas like theorem proving, model checking, automata and logic, process algebra, and constraint solving. In this introduction to the special issue, dedicated to a selection of works from the Parameterized Verification workshop PV \u201914 and PV \u201915, we survey some of the works developed in this research area
Event analytics
The process analysis toolkit (PAT) integrates the expressiveness of state, event, time, and probability-based languages with the power of model checking. PAT is a self-contained reasoning system for system specification, simulation, and verification. PAT currently supports a wide range of 12 different expressive modeling languages with many application domains and has attracted thousands of registered users from hundreds of organizations. In this invited talk, we will present the PAT system and its vision on “Event Analytics” (EA) which is beyond “Data Analytics”. The EA research is based on applying model checking to event planning, scheduling, prediction, strategy analysis and decision making. Various new EA research directions will be discussed.No Full Tex
Removing Algebraic Data Types from Constrained Horn Clauses Using Difference Predicates
We address the problem of proving the satisfiability of Constrained Horn
Clauses (CHCs) with Algebraic Data Types (ADTs), such as lists and trees. We
propose a new technique for transforming CHCs with ADTs into CHCs where
predicates are defined over basic types, such as integers and booleans, only.
Thus, our technique avoids the explicit use of inductive proof rules during
satisfiability proofs. The main extension over previous techniques for ADT
removal is a new transformation rule, called differential replacement, which
allows us to introduce auxiliary predicates corresponding to the lemmas that
are often needed when making inductive proofs. We present an algorithm that
uses the new rule, together with the traditional folding/unfolding
transformation rules, for the automatic removal of ADTs. We prove that if the
set of the transformed clauses is satisfiable, then so is the set of the
original clauses. By an experimental evaluation, we show that the use of the
differential replacement rule significantly improves the effectiveness of ADT
removal, and we show that our transformation-based approach is competitive with
respect to a well-established technique that extends the CVC4 solver with
induction.Comment: 10th International Joint Conference on Automated Reasoning (IJCAR
2020) - version with appendix; added DOI of the final authenticated Springer
publication; minor correction
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
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