Juergen Dingel

A survey of self-management in dynamic software architecture specifications

As dynamic software architecture use becomes more widespread, a variety of formal specification languages have been developed to gain a better understanding of the foundations of this type of software evolutionary change. In this paper we survey 14 formal specification approaches based on graphs, process algebras, logic, and other formalisms. Our survey will evaluate the ability of each approach to specify self-managing systems as well as the ability to address issues regarding expressiveness and scalability. Based on the results of our survey we will provide recommendations on future directions for improving the specification of dynamic software architectures, specifically self-managed architectures.

UML vs. classical vs. rhapsody statecharts: not all models are created equal

State machines, represented by statecharts or state machine diagrams, are an important formalism for behavioural modelling. According to the research literature, the most popular statechart formalisms appear to be Classical, UML, and that implemented by Rhapsody. These three formalisms seem to be very similar; however, there are several key syntactic and semantic differences. These differences are enough that a model written in one formalism could be ill-formed in another formalism. Worse, a model from one formalism might actually be well-formed in another, but be interpreted differently due to the semantic differences. This paper summarizes the results of an informal comparative study of these three formalisms with the help of several illustrative examples. We present a classification of the differences according to the nature of potential problems caused by each difference. In addition, for each difference we discuss how translation between formalisms can be achieved, if at all.

A comparative survey of scenario-based to state-based model synthesis approaches

Model Driven Development and Use Case Driven Development methodologies have inspired the proposal of a variety of software engineering approaches that synthesize state-based models from scenario-based models. However, little work has been done to comprehensively compare these different synthesis approaches. In this paper, we define a set of comparison criteria, and survey 21 different synthesis approaches presented in the literature based on the criteria. The differences and similarities are highlighted in the comparison results. We then discuss the challenges that current approaches may face and provide suggestions for future work for state-based model syntheses.

Reasoning about implicit invocation

Implicit invocation [SN92, GN91] has become an important architectural style for large-scale system design and evolution. This paper addresses the lack of specification and verification formalisms for such systems. Based on standard notions from process algebra and trace semantics, we define a formal computational model for implicit invocation. A verification methodology is presented that supports linear time temporal logic and compositional reasoning. First, the entire system is partioned into groups of components (methods) that behave independently. Then, local properties are proved for each of the groups. A precise description of the cause and the effect of an event supports this step. Using local correctness, independence of groups, and properties of the delivery of events, we infer the desired property of the overall system. Two detailed examples illustrate the use of our framework.

Model transformation intents and their properties

The notion of model transformation intent is proposed to capture the purpose of a transformation. In this paper, a framework for the description of model transformation intents is defined, which includes, for instance, a description of properties a model transformation has to satisfy to qualify as a suitable realization of an intent. Several common model transformation intents are identified, and the framework is used to describe six of them in detail. A case study from the automotive industry is used to demonstrate the usefulness of the proposed framework for identifying crucial properties of model transformations with different intents and to illustrate the wide variety of model transformation intents that an industrial model-driven software development process typically encompasses.

Evaluating and improving the automatic analysis of implicit invocation systems

Model checking and other finite-state analysis techniques have been very successful when used with hardware systems and less successful with software systems. It is especially difficult to analyze software systems developed with the implicit invocation architectural style because the loose coupling of their components increases the size of the finite state model. In this paper we provide insight into the larger problem of how to make model checking a better analysis and verification tool for software systems. Specifically, we will extend an existing approach to model checking implicit invocation to allow for the modeling of larger and more realistic systems. Our focus will be on improving the representation of events, event delivery policies and event-method bindings. We also evaluate our technique on two non-trivial examples. In one of our examples, we will show how with iterative analysis a system parameter can be chosen to meet the appropriate system requirements.

Package merge in UML 2: practice vs. theory?

The notion of compliance is meant to facilitate tool interoperability. UML 2 offers 4 compliance levels. Level Li+1 is obtained from Level Li through an operation called package merge. Package merge is intended to allow modeling concepts defined at one level to be extended with new features. To ensure interoperability, package merge has to ensure compatibility: the XMI representation of the result of the merge has to be compatible with that of the original package. UML 2 lacks a precise and comprehensive definition of package merge. This paper reports on our work to understand and formalize package merge. Its main result is that package merge as defined in UML 2.1 does not ensure compatibility. To expose the problem and possible remedies more clearly, we present this result in terms of a very general classification of model extension mechanisms.

Generation of concurrency control code using discrete-event systems theory

The development of controls for the execution of concurrent code is non-trivial. We show how existing discrete-event system (DES) theory can be successfully applied to this problem. From code without concurrency controls and a specification of desired behaviours, concurrency control code is generated. By applying rigorously proven DES theory, we guarantee that the control scheme is nonblocking (and thus free of both deadlock and livelock) and minimally restrictive. Some conflicts between specifications and source can be automatically resolved without introducing new specifications. Moreover, the approach is independent of specific programming or specification languages. Two examples using Java are presented to illustrate the approach. Additional applicable DES results are discussed as future work.

Towards a UML virtual machine: implementing an interpreter for UML 2 actions and activities

An interpreter for UML 2 actions and activities is presented. It is based on two novel features in UML 2: the three-layer semantics architecture and the new token offer semantics for activities, which is intended to generalize the token flow semantics of Petri nets. The interpreter offers an array of analysis capabilities, ranging from random execution to reachability properties and assertion and deadlock checking. The design of the interpreter makes it suitable as the basis for a more comprehensive UML virtual machine.

2nd UML 2 semantics symposium: formal semantics for UML

The purpose of this symposium, held in conjunction with MoDELS 2006, was to present the current state of research of the UML 2 Semantics Project. Equally important to receiving feedback from an audience of experts was the opportunity to invite researchers in the field to discuss their own work related to a formal semantics for the Unified Modeling Language. This symposium is a follow-on to our first workshop, held in conjunction with ECMDA 2005.