Extending the theory of Owicki and Gries with a logic of progress

This paper describes a logic of progress for concurrent programs. The logic is based on that of UNITY, molded to fit a sequential programming model. Integration of the two is achieved by using auxiliary variables in a systematic way that incorporates program counters into the program text. The rules for progress in UNITY are then modified to suit this new system. This modification is however subtle enough to allow the theory of Owicki and Gries to be used without change

Trace Semantics for the Owicki-Gries Theory Integrated with the Progress Logic from UNITY

The theory of Owicki and Gries has been used as a platform for safety-based verifcation and derivation of concurrent programs. It has also been integrated with the progress logic of UNITY which has allowed newer techniques of progress-based verifcation and derivation to be developed. However, a theoretical basis for the integrated theory has thus far been missing. In this paper, we provide a theoretical background for the logic of Owicki and Gries integrated with the logic of progress from UNITY. An operational semantics for the new framework is provided which is used to prove soundness of the progress logic

Concurrent Program Design in the Extended Theory of Owicki and Gries

Feijen and van Gasteren have shown how to use the theory of Owicki and Gries to design concurrent programs, however, the lack of a formal theory of progress has meant that these designs are driven entirely by safety requirements. Proof of progress requirements are made post-hoc to the derivation and are operational in nature. In this paper, we describe the use of an extended theory of Owicki and Gries in concurrent program design. The extended theory incorporates a logic of progress, which provides opportunity to develop a program in a manner that gives proper consideration to progress requirements. Dekker's algorithm for two process mutual exclusion is chosen to illustrate the use of the extended theory

Streamlining Progress-Based Derivations of Concurrent Programs

The logic of Owicki and Gries is a well known logic for verifying safety properties of concurrent programs. Using this logic, Feijen and van Gasteren describe a method for deriving concurrent programs based on safety. In this work, we explore derivation techniques of concurrent programs using progress-based reasoning. We use a framework that combines the safety logic of Owicki and Gries, and the progress logic of UNITY. Our contributions improve the applicability of our earlier techniques by reducing the calculational overhead in the formal proofs and derivations. To demonstrate the effectiveness of our techniques, a derivation of Dekker's mutual exclusion algorithm is presented. This derivation leads to the discovery of some new and simpler variations of this famous algorithm

Contributions of formal language theory to the study of dialogues

For more than 30 years, the problem of providing a formal framework for modeling dialogues has been a topic of great interest for the scientific areas of Linguistics, Philosophy, Cognitive Science, Formal Languages, Software Engineering and Artificial Intelligence. In the beginning the goal was to develop a "conversational computer", an automated system that could engage in a conversation in the same way as humans do. After studies showed the difficulties of achieving this goal Formal Language Theory and Artificial Intelligence have contributed to Dialogue Theory with the study and simulation of machine to machine and human to machine dialogues inspired by Linguistic studies of human interactions. The aim of our thesis is to propose a formal approach for the study of dialogues. Our work is an interdisciplinary one that connects theories and results in Dialogue Theory mainly from Formal Language Theory, but also from another areas like Artificial Intelligence, Linguistics and Multiprogramming. We contribute to Dialogue Theory by introducing a hierarchy of formal frameworks for the definition of protocols for dialogue interaction. Each framework defines a transition system in which dialogue protocols might be uniformly expressed and compared. The frameworks we propose are based on finite state transition systems and Grammar systems from Formal Language Theory and a multi-agent language for the specification of dialogue protocols from Artificial Intelligence. Grammar System Theory is a subfield of Formal Language Theory that studies how several (a finite number) of language defining devices (language processors or grammars) jointly develop a common symbolic environment (a string or a finite set of strings) by the application of language operations (for instance rewriting rules). For the frameworks we propose we study some of their formal properties, we compare their expressiveness, we investigate their practical application in Dialogue Theory and we analyze their connection with theories of human-like conversation from Linguistics. In addition we contribute to Grammar System Theory by proposing a new approach for the verification and derivation of Grammar systems. We analyze possible advantages of interpreting grammars as multiprograms that are susceptible of verification and derivation using the Owicki-Gries logic, a Hoare-based logic from the Multiprogramming field

Constructive formal methods and protocol standardization

This research is part of the NWO project "Improving the Quality of Protocol Standards". In this project we have cooperated with industrial standardization committees that are developing protocol standards. Thus we have contributed to these international standards, and we have generated relevant research questions in the field of formal methods. The first part of this thesis is related to the ISO/IEEE 1073.2 standard, which addresses medical device communication. The protocols in this standard were developed from a couple of MSC scenarios that describe typical intended behavior. Upon synthesizing a protocol from such scenarios, interference between these scenarios may be introduced, which leads to undesired behaviors. This is called the realizability problem. To address the realizability problem, we have introduced a formal framework that is based on partial orders. In this way the problem that causes the interference can be clearly pointed out. We have provided a complete characterization of realizability criteria that can be used to determine whether interference problems are to be expected. Moreover, we have provided a new constructive approach to solve the undesired interference in practical situations. These techniques have been used to improve the protocol standard under consideration. The second part of this thesis is related to the IEEE 1394.1-2004 standard, which addresses High Performance Serial Bus Bridges. This is an extension of the IEEE 1394-1995 standard, also known as FireWire. The development of the distributed spanning tree algorithm turned out to be a serious problem. To address this problem, we have first developed and proposed a much simpler algorithm. We have also studied the algorithm proposed by the developers of the standard, namely by formally reconstructing a version of it, starting from the specification. Such a constructive approach to verification and analysis uses mathematical techniques, or formal methods, to reveal the essential mechanisms that play a role in the algorithm. We have shown the need for different levels of abstraction, and we have illustrated that the algorithm is in fact distributed at two levels. These techniques are usually applied manually, but we have also developed an approach to automate parts of it using state-of-the-art theorem provers

A framework for automated concurrency verification

Reasoning systems based on Concurrent Separation Logic make verifying complex concurrent algorithms readily possible. Such algorithms contain subtle protocols of permission and resource transfer between threads; to cope with these intricacies, modern concurrent separation logics contain many moving parts and integrate many bespoke logical components. Verifying concurrent algorithms by hand consumes much time, effort, and expertise. As a result, computer-assisted verification is a fertile research topic, and fully automated verification is a popular research goal. Unfortunately, the complexity of modern concurrent separation logics makes them hard to automate, and the proliferation and fast turnover of such logics causes a downward pressure against building tools for new logics. As a result, many such logics lack tooling. This dissertation proposes Starling: a scheme for creating concurrent program logics that are automatable by construction. Starling adapts the existing Concurrent Views Framework for sound concurrent reasoning systems, overlaying a framework for reducing concurrent proof outlines to verification conditions in existing theories (such as those accepted by off-the-shelf sequential solvers). This dissertation describes Starling in a bottom-up, modular manner. First, it shows the derivation of a series of general concurrency proof rules from the Views framework. Next, it shows how one such rule leads to the Starling framework itself. From there, it outlines a series of increasingly elaborate frontends: ways of decomposing individual Hoare triples over atomic actions into verification conditions suitable for encoding into backend theories. Each frontend leads to a concurrent program logic. Finally, the dissertation presents a tool for verifying C-style concurrent proof outlines, based on one of the above frontends. It gives examples of such outlines, covering a variety of algorithms, backend solvers, and proof techniques