6090717
From Testing Theory to Test Driver Implementation
In this article we describe the theoretical foundations for the VVT-RT test system (Verification, Validation and Test for Reactive Real-Time Systems) which supports automated test generation, test execution and test evaluation for reactive systems. VVT-RT constructs and evaluates tests based on formal CSP specifications [6], making use of their representation as labelled transition systems generated by the CSP model checker FDR [3]. The present article provides a sound formal basis for the development and verification of high-quality test tools: Since, due to the high degree of automation offered by VVT-RT, human interaction becomes superfluous during critical phases of the test process, the trustworthiness of the test tool is an issue of great importance. The VVT-RT system will therefore be formally verified so that it can be certified for testing safety-critical systems. The present article represents the starting point of this verification suite, where the basic strategies for test generation and test evaluation used by the system are formally described and verified. VVT-RT has been designed to support automation of both untimed and real-time tests. The present article describes the underlying theory for the untimed case. Exploiting these results, the concepts and high-level algorithms used for the automation of real-time tests are described in a second report which is currently prepared [14]. At present, VVT-RT is applied for hardware-in-the-loop tests of railway and tramway control computers.
39950733
A Refinement Theory that Supports both 'Decrease of Nondeterminism' and 'Increase of Parallelism'
The decrease of nondeterminism development paradigm that underlies most refinement approaches for concurrent systems is contrasted with the less studied increase of parallelism paradigm used by many protocol designers. We show that the widely used refinement notion of Abadi & Lamport exclusively supports the first paradigm and formulate a generalization that allows derivations of systems applying both paradigms alternatively. We develop the proof technique delayed simulation to prove Abadi & Lamport refinement and its generalization.
33236770
Formal Verification of Stabilizing Systems
This paper links too formerly rather disjoint areas: formal verification and stabilization. Stabilization is a vitally emerging paradigm in fault tolerant distributed computing; formal verification investigates mathematically rigorous techniques to reason about systems.
1155385
Implementing statecharts in PROMELA/SPIN
We translate statecharts into PROMELA, the input language of the SPIN verification system, using extended hierarchical automata as an intermediate format. We discuss two possible frameworks for this translation, leading to either sequential or parallel code. We show that in this context the sequential code can be verified more efficiently than the parallel code. We conclude with a discussion of an application of the resulting translator to a well-known case study, which demonstrates the feasibility of linear temporal logic model checking of statecharts.
6836947
Deductive verification of stabilizing systems
17738680
Hierarchical Automata as Model for Statecharts
Statecharts are a very rich graphical specification formalism supported by the commercial tool Statemate. Statecharts comprises powerful concepts such as interlevel transitions, multiple-source/multiple-target transitions, priority amongst transitions and simultaneous execution of maximal non-conflicting sets of transitions. Every add-on tool which is supposed to be linked with the Statemate tool have to deal with the rather involved semantics of these concepts. We propose extended hierarchical automata as an intermediate format to facilitate the linking of new tools to the Statemate environment, whose main idea is to devise a simple formalism with a more restricted syntax than statecharts which nevertheless allows to capture the richer formalism. We define the format, give operational semantics to it, and translate statecharts to it.
38159603
The COntext INterchange (COIN) Project: Data Extraction and Interpretation from Semi-Structured Web Sources
41563606
Conceptualizing Semantic Interoperability: A Perspective From the Knowledge Level
Currently, there is a proliferation of database integration approaches in response to the need to achieve semantic interoperability in heterogeneous, distributed and autonomous environments. To date, however, we lack abstract, formal descriptions of the task of semantic interoperation, independent of idiosyncratic implementation details. Such abstract descriptions are needed to aid our understanding of these various complex systems that are being constructed. Therefore, we argue that a knowledge level perspective of interoperable systems is desirable. The knowledge level serves as an abstract specification of what a system should do and facilitates the design and analysis of complex systems. In this paper, we show how an interoperable system, based on the Context Interchange Architecture, may be specified in terms of first-order logic which is an ideal specification language at the knowledge level. This specification represents a theoretical ideal which serves to formalize and communicate the key ideas behind the Context Interchange Approach, unencumbered by the details, limitations and compromises of specific implementations. As such, it provides a rigorous basis for implementing such systems. Similar specifications may also be developed for other models of interoperable systems. As a result, we have a rigorous means of understanding, comparing and analyzing these complex systems.
15882359
Deciding Equality Formulas by Small Domains Instantiations
We introduce an efficient decision procedure for the theory of equality based on finite instantiations. When using the finite instantiations method, it is a common practice to take a range of [1..n] (where n is the number of input non-Boolean variables) as the range for all non-Boolean variables, resulting in a state-space of nn. Although various attempts to minimize this range were made, typically they either required various restrictions on the investigated formulas or were not very effective. In many cases, the nn state-space cannot be handled by BDD-based tools within a reasonable amount of time. In this paper we show that significantly smaller domains can be algorithmically found, by analyzing the structure of the formula. We also show an upper bound for the state-space based on this analysis. This method enabled us to verify formulas containing hundreds of integer and floating point variables.
653091
A method for automatic rule derivation to support semantic query optimization
The use of inference rules to support intelligent data processing is an increasingly important tool in many areas of computer science. In database systems, rules are used in semantic query optimization as a method for reducing query processing costs. The savings is dependent on the ability of experts to supply a set of useful rules and the ability of the optimizer to quickly find the appropriate transformations generated by these rules. Unfortunately, the most useful rules are not always those that would or could be specified by an expert. This paper describes the architecture of a system having two interrelated components: a combined conventional/semantic query optimizer, and an automatic rule deriver.
Our automatic rule derivation method uses intermediate results from the optimization process to direct the search for learning new rules. Unlike a system employing only user-specified rules, a system with an automatic capability can derive rules that may be true only in the current state of the database and can modify the rule set to reflect changes in the database and its usage pattern.
This system has been implemented as an extension of the EXODUS conventional query optimizer generator. We describe the implementation, and show how semantic query optimization is an extension of conventional optimization in this context.
122171625
The small model property: how small can it be?
Efficient decision procedures for equality logic (quantifier-free predicate calculus + the equality sign) are of major importance when proving logical equivalence between systems. We introduce an efficient decision procedure for the theory of equality based on finite instantiations. The main idea is to analyze the structure of the formula and compute accordingly a small domain to each variable such that the formula is satisfiable iff it can be satisfied over these domains. We show how the problem of finding these small domains can be reduced to an interesting graph theoretic problem. This method enabled us to verify formulas containing hundreds of integer and floating point variables that could not be efficiently handled with previously known techniques.