Towards a new extension relation for compositional test case generation for CSP concurrent processes

Abstract

Software concurrent systems such as electronic financial services are very popular today. Rigorous testing of such systems is indispensable. Nevertheless, the state-explosion problem, in which the size of a system grows exponentially with the number of concurrent components, is a severe obstacle to the generation of test cases.In this study, we propose a new relationship assuring the conformities of test cases for concurrent systems. We stipulate it in Communicating Sequential Processes (CSP), which is an excellent tool to study concurrent systems. Specification of concurrent systems is expressed as processes that are composed sequentially and concurrently. Our proposal supports both abstraction and process composition.This approach decomposes a given process into sequential compositions of component processes. Each component can be anti-extended into abstract forms. Sequential and concurrent combinations of abstract forms can substitute their corresponding extending components in a process to form aggregated abstract forms. Since the given processes, components and abstract forms are all processes, this approach can be applied recursively and compositionally. We prove that these aggregated abstract processes should be anti-extensions of the corresponding processes under a few necessary and sufficient conditions. Hence, test cases generated from these processes will be conformance test cases for the implementations.We examine three major testing relations (conformance, extension and reduction) from the point of view of their ability to support abstraction. Extension and reduction are special kinds of conformance, which are partially ordered. However, only extension from a specification can provide abstract forms that guarantee to be conformed by an implementation of the specification. Extension is further investigated to support the compositional approach. We identify five weaknesses of extension, which we call problems of preceding, succeeding, prefix, decomposition and paralleling. Each will result in non-conforming abstraction.To resolve the identified weaknesses of extension in a compositional and abstractionoriented approach, we formulate σ-extension and identify the necessary and sufficient conditions. We also discuss a restricted sub-class of process specification so that these conditions can easily be satisfied. In the restricted sub-class, successful terminations of processes are deterministic.Under these conditions, we achieve a few desirable properties. First, both preceding and succeeding components of a given sequential composition can be anti-extended. The given composition should extend the sequential composition of its corresponding anti-extended processes. Secondly, a given parallel composition whose concurrent components are sequential compositions should extend a parallel composition of anti-extensions of preceding components of corresponding sequential compositions, followed by a parallel composition of anti-extensions of corresponding succeeding components. Furthermore, a given sequential co...

Sequential paraformaldehyde and methanol fixation for simultaneous flow cytometric analysis of DNA, cell surface proteins, and intracellular proteins

“…Unfortunately, no clear consensus has emerged from these studies with regard to optimal cell fixation conditions for multiparameter flow cytometric analysis. In a number of studies, cells were fixed in methanol alone (8,15,19) or ethanol alone (1,3,7,9,10,16,18,25). However, comparative studies of alcohol with paraformaldehyde fixation have sug-gested that there may be significant loss of cytoplasmic or nuclear proteins from cells following fixation with alcohol alone (17,181. Formaldehyde-based fixation procedures have varied widely among published studies.…”