A framework for pathologies of message sequence charts

Abstract

Context: It is known that a Message Sequence Chart (MSC) specification can contain different types of pathology. However, definitions of different types of pathology and the problems caused by pathologies are unclear, let alone the relationships between them. In this circumstance, it can be problematic for software engineers to accurately predict the possible problems that may exist in implementations of MSC specifications and to trace back to the design problems in MSC specifications from the observed problems of an implementation. Objective: We focus on generating a clearer view on MSC pathologies and building formal relationships between pathologies and the problems that they may cause. Method: By concentrating on the problems caused by pathologies, a categorisation of problems that a distributed system may suffer is first introduced. We investigate the different types of problems and map them to a categories of pathologies. Thus, existing concepts related to pathology are refined and necessary concepts in the pathology framework are identified. Finally, we formally prove the relationships between the concepts in the framework. Results: A pathology framework is established as desired based on a restriction that considers problematic scenarios with a single undesirable event. In this framework, we define disjoint categories of both pathologies and the problems caused; the identified types of pathology are successfully mapped to the problems that they may cause. Conclusion: The framework achieved in this paper introduces taxonomies into and clarifies relationships between concepts in research on MSC pathologies. The taxonomies and relationships in the framework can help software engineers to predict problems and verify MSC specifications. The single undesirable event restriction not only enables a categorisation of pathological scenarios, but also has the potential practical benefit that a software engineer can concentrate on key problematic scenarios. This may make it easier to either remove pathologies from an MSC specification M or test an implementation developed from M for potential problems resulting from such pathologies.

The Oracle Problem When Testing from MSCs

“…This complements previous results suggesting that the semantics of scenario-based models can be difficult to understand, leading to the potential for subtle mistakes [18]. A tester wishing to base testing on MSCs must consider the semantic issue and the results in this paper also show that the set of features used can have another significant practical effect in that it influences the computational complexity of the Oracle Problem.…”

“…It has been shown that the notion of a controllability problem when testing from an MSC specification is related to MSC pathologies [18]. In this paper, we discuss another critical issue in conformance testing with MSCs: the Oracle Problem.…”

“…Possible controllability problems have to be resolved in running distributed tests so that correct input is sent to the SUT. A test coordinator may help to overcome the controllability problem by sending and receiving additional control messages [18]. We have to solve the Oracle Problem when we have made observations in testing and wish to assign a verdict that states whether a failure has occurred.…”

Semantic Studies of a Synchronous Approach to Activity Recognition

“…The MSC operators and the hierarchical composition of HMSCs are similar to our approach. However, [15] reveals "pathologies" in MSCs, due to defective MSC specifications. These pathologies mainly affect synchronization issues.…”

Controllability Problems in MSC-Based Testing

“…This is in contrast to other popular behaviour models such as Finite State Machines (FSMs) and Input/Output Labelled Transition Systems (IOLTSs) [22,23,24,25]. This seems surprising since there has been much interest in the use of MSCs and analysing MSCs to, for example, find pathologies [26,4,27,28,29,30,31,32]. As MSCs are popular in modelling distributed systems, they have the potential to play an important role in MBT for distributed systems including systems based on grid and cloud technologies.…”