A Polynomial Translation of pi-calculus FCPs to Safe Petri Nets

We develop a polynomial translation from finite control pi-calculus processes to safe low-level Petri nets. To our knowledge, this is the first such translation. It is natural in that there is a close correspondence between the control flows, enjoys a bisimulation result, and is suitable for practical model checking.Comment: To appear in special issue on best papers of CONCUR'12 of Logical Methods in Computer Scienc

Towards Intelligent Databases

This article is a presentation of the objectives and techniques of deductive databases. The deductive approach to databases aims at extending with intensional definitions other database paradigms that describe applications extensionaUy. We first show how constructive specifications can be expressed with deduction rules, and how normative conditions can be defined using integrity constraints. We outline the principles of bottom-up and top-down query answering procedures and present the techniques used for integrity checking. We then argue that it is often desirable to manage with a database system not only database applications, but also specifications of system components. We present such meta-level specifications and discuss their advantages over conventional approaches

Automatic Verification of Erlang-Style Concurrency

This paper presents an approach to verify safety properties of Erlang-style, higher-order concurrent programs automatically. Inspired by Core Erlang, we introduce Lambda-Actor, a prototypical functional language with pattern-matching algebraic data types, augmented with process creation and asynchronous message-passing primitives. We formalise an abstract model of Lambda-Actor programs called Actor Communicating System (ACS) which has a natural interpretation as a vector addition system, for which some verification problems are decidable. We give a parametric abstract interpretation framework for Lambda-Actor and use it to build a polytime computable, flow-based, abstract semantics of Lambda-Actor programs, which we then use to bootstrap the ACS construction, thus deriving a more accurate abstract model of the input program. We have constructed Soter, a tool implementation of the verification method, thereby obtaining the first fully-automatic, infinite-state model checker for a core fragment of Erlang. We find that in practice our abstraction technique is accurate enough to verify an interesting range of safety properties. Though the ACS coverability problem is Expspace-complete, Soter can analyse these verification problems surprisingly efficiently.Comment: 12 pages plus appendix, 4 figures, 1 table. The tool is available at http://mjolnir.cs.ox.ac.uk/soter

Requirements modelling of real-time systems

Real-time systems are characterised by the critical nature of their missions, and the demanding environment with which they interact. Real-time systems are used for dedicated applications. Every application is the subject of special requirements enforced by the customer. Considering the vital role that these systems play, it is imperative that a systematic approach be adopted in modelling their unique requirements. In this thesis I propose such a treatment. Real-time systems are time critical. Temporal requirements are the timing restrictions imposed by the application environment. Previous studies in requirements modelling of real-time systems have focused on adding the notion of time to modelling techniques of traditional systems without regard to the realities of requirements modelling. The information should be presented in the way the user handles it, and not the way which is convenient to the software engineer. I attempt to understand the needs of the users better by modelling the real world as close to the user's perspective as possible, and propose the Real World Model (RWM). RWM is assumed to be developed by users, and requirements engineers. An engineering approach to building the model is provided. A real-time system has a well defined use to its community. A requirements model must rely on the user level activities, and aid the human understanding and communication. In the RWM, a real-time system is viewed as a set of concurrently acting automata, each representing a system entity. This model supports temporal reasoning in easily described ways, for all classes of timing properties. A generalised classification of timing constraints is provided. A requirements modelling language facilitates the description of requirements, and serves as a medium of communication among developers and stakeholders. Jarke et al [Jarke 94] observe that there is a need for a requirements language that manages the relationship between the meta-level domain scheme, and the scenarios that actually instantiate the scheme under development. Here I propose Timed Requirements Language (TRL) to bridge this gulf between the world of stakeholders, and the world of specifiers. TRL has natural looking expressions for formulating the needs. TRL has a number of novel features including the treatment of causality, and the description of static, and dynamic constraints all integrated into one uniform framework. TRL has been used with a number of systems. The generality of the language is validated through its application to specific systems