Architecting families of software systems with process algebras

Abstract

Software components can give rise to several kinds of architectural mismatches when assembled together in order to form a software system. A formal description of the architecture of the resulting component based software system may help to detect such architectural mismatches and to single out the components that cause the mismatches. In this paper we concentrate on deadlock related architectural mismatches arising from three different causes that we identify: incompatibility between two components due to a single interaction, incompatibility between two components due to the combination of several interactions, and lack of interoperability among a set of components forming a cyclic topology. We develop a process algebra based architectural description language called PADL, which deals with all the three causes through an architectural compatibility check and an architectural interoperability check relying on standard observational equivalences. The adequacy of the architectural compatibility check is assessed on a compressing proxy system, while the adequacy of the architectural interoperability check is assessed on a cruise control system. We then address the issue of scaling the architectural compatibility and interoperability checks to architectural styles through an extension of PADL. The formalization of an architectural style is complicated by the presence of two degrees of freedom within the set of instances of the style: variability of the internal behavior of the components and variability of the topology formed by the components. As a first step towards the solution of the problem, we propose an intermediate abstraction called architectural type, whose instances differ only for the internal behavior of their components. We define an efficient architectural conformity check based on a standard observational equivalence to verify whether an architecture is an instance of an architectural type. We show that all the architectures conforming to the same architectural type possess the same compatibility and interoperability properties.

Consistency and interoperability checking for component interaction rules

“…Thus a component cannot block inputs from happening before it is ready to process them. The adoption of this composition mechanism enables optimistic reasoning of partially built (or open) systems and differentiates our approach from many existing component specification approaches such as [1,4,6,21,22,24].…”

“…A considerable number of formal language based approaches have been proposed in the literature to overcome the ambiguity of informal documentation used in the industry. For example, [7,9,22,24] use finite state machines (FSMs), [2,8] interface automata, [1,4,6] process algebra, [21] regular expressions, [3] Petri nets, and [5] description logics. The benefit of using a well-developed language is that many analysis In contrast, our specification approach is designed for use by software practitioners.…”

“…Unlike approaches that require the user encode all interaction rules of a component into a single protocol model, e.g. [3,4,6,7,8,9,21,24], our work allows for relatively independent and declarative specification of these rules. This idea originates from [15,16].…”

Predictable Dynamic Plugin Systems

“…Several ADLs have been extended or complemented with languages for describing behaviour, for example C2SADEL [11] which uses logic to specify behaviour, or Wright [6] and PADL [3] which use process algebra.…”

Preserving Architectural Properties in Multithreaded Code Generation

“…Whenever such a document is made formal through the use of a suitable architectural description language (ADL), an early assessment of the gross system properties can be carried out. This is the case with process algebraic ADLs, for which several techniques based on equivalence checking have been developed for the component-oriented verification and diagnosis of architectural mismatch freedom [3,11,10,9,6,5,1].…”