Jochen Malte Küster

Confluence of Typed Attributed Graph Transformation Systems

The issue of confluence is of major importance for the successful application of attributed graph transformation, such as automated translation of UML models into semantic domains. Whereas termination is undecidable in general and must be established by carefully designing the rules, local confluence can be shown for term rewriting and graph rewriting using the concept of critical pairs. In this paper, we discuss typed attributed graph transformation using a new simplified notion of attribution. For this kind of attributed graph transformation systems we establish a definition of critical pairs and prove a critical pair lemma, stating that local confluence follows from confluence of all critical pairs.

Generation of business process models for object life cycle compliance

Business process models usually capture data exchanged betweentasks in terms of objects. These objects are commonly standardizedusing reference data models that prescribe, among other things, allowedobject states. Allowed state transitions can be modeled as objectlife cycles that require compliance of business processes. In this paper, wefirst establish a notion of compliance of a business process model with anobject life cycle. We then propose a technique for generating a compliantbusiness process model from a set of given reference object life cycles.

Detecting and Resolving Process Model Differences in the Absence of a Change Log

Business-driven development favors the construction of process models at different abstraction levels and by different people. As a consequence, there is a demand for consolidating different versions of process models by detecting and resolving differences. Existing approaches rely on the existence of a change log which logs the changes when changing a process model. However, in several scenarios such a change log does not exist and differences must be identified by comparing process models before and after changes have been made. In this paper, we present our approach to detecting and resolving differences between process models, in the absence of a change log. It is based on computing differences and deriving change operations for resolving differences, thereby providing a foundation for variant and version management in these cases.

A methodology for specifying and analyzing consistency of object-oriented behavioral models

Object-oriented modeling favors the modeling of object behavior from different viewpoints and the successive refinement of behavioral models in the development process. This gives rise to consistency problems of behavioral models. The absence of a formal semantics for UML models and the numerous possibilities of employing behavioral models within the development process lead to the rise of a number of different consistency notions. In this paper, we discuss the issue of consistency of behavioral models in the UML and present a general methodology how consistency problems can be dealt with. According to the methodology, those aspects of the models relevant to the consistency are mapped to a semantic domain in which precise consistency tests can be formulated. The choice of the semantic domain and the definition of consistency conditions can be used to construct different consistency notions. We show the applicability of our methodology by giving an example of a concrete consistency problem of concurrent object-oriented models.

Generating instance models from meta models

Meta modeling is a wide-spread technique to define visual languages, with the UML being the most prominent one. Despite several advantages of meta modeling such as ease of use, the meta modeling approach has one disadvantage: it is not constructive, i.e., it does not offer a direct means of generating instances of the language. This disadvantage poses a severe limitation for certain applications. For example, when developing model transformations, it is desirable to have enough valid instance models available for large-scale testing. Producing such a large set by hand is tedious. In the related problem of compiler testing, a string grammar together with a simple generation algorithm is typically used to produce words of the language automatically. In this paper, we introduce instance-generating graph grammars for creating instances of meta models, thereby overcoming the main deficit of the meta modeling approach for defining languages.

Rule-Based Specification of Behavioral Consistency Based on the UML Meta-model

Object-oriented modeling favors the modeling of object behavior from different viewpoints and at different levels of abstraction. This gives rise to consistency problems between overlapping or semantically related submodels. The absence of a formal semantics for the UML and the numerous ways of employing the language within the development process lead to a number of different consistency notions. Therefore, general meta-level techniques are required for specifying, analyzing, and communicating consistency constraints. In this paper, we discuss the issue of consistency of behavioral models in the UML and present techniques for specifying and analyzing consistency. Using meta-model rules we transform elements of UML models into a semantic domain. Then, consistency constraints can by specified and validated using the language and the tools of the semantic domain. This general methodology is exemplified by the problem of protocol statechart inheritance.

Definition and validation of model transformations

With model transformations becoming more widely used, there is an increasing need for approaches focussing on a systematic development of model transformations. Although a number of approaches for specifying model transformations exist, none of them focusses on systematically validating model transformations with respect to termination and confluence. Termination and confluence ensure that a model transformation always produces a unique result. Also called functionality, these properties are important requirements for practical applications of model transformations. In this paper, we introduce our approach to model transformation. Using and extending results from the theory of graph transformation, we investigate termination and confluence properties of model transformations specified in our approach. We establish a set of criteria for termination and confluence to be checked at design time by static analysis of the transformation rules and the underlying metamodels. Moreover, the criteria are formulated in such a way that they require less experience with the theory of graph transformation. Our concepts are illustrated by a running example of a model tranformation from statecharts to the process algebra Communicating Sequential Processes.

Reusable architectural decision models for enterprise application development

In enterprise application development and other software construction projects, a critical success factor is to make sound architectural decisions. Text templates and tool support for capturing architectural decisions exist, but have failed to reach broad adoption so far. One of the inhibitors we perceived on large-scale industry projects is that architectural decision capturing is regarded as a retrospective and therefore unwelcome documentation task which does not provide any benefit during the original design work. A major problem of such a retrospective approach is that the decision rationale is not available to decision makers when they identify, make, and enforce decisions. Often a large, possibly distributed, community of decision makers is involved in these three steps. In this paper, we propose a new conceptual framework for proactive decision identification, decision maker collaboration, and decision enforcement. Based on a meta model capturing reuse and collaboration aspects explicitly, our framework instantiates decision models from requirements models and reusable decision templates. These templates capture knowledge gained on other projects employing the same architectural style. As an exemplary application of these concepts to service-oriented architecture shows, reusable architectural decision models can speed up the decision identification and improve the quality of the decision making. Reusable architectural decision models can also simplify the exchange of architecture design rationale within and between project teams, and expose decision outcome as model transformation parameters in model-driven software development.

Validation of model transformations: first experiences using a white box approach

Validation of model transformations is important for ensuring their quality. Successful validation must take into account the characteristics of model transformations and develop a suitable fault model on which test case generation can be based. In this paper, we report our experiences in validating a number of model transformations and propose three techniques that can be used for constructing test cases.

The Role of Visual Modeling and Model Transformations in Business-driven Development

This paper explores the emerging paradigm of business-driven development, which presupposes a methodology for developing IT solutions that directly satisfy business requirements and needs. At the core of business-driven development are business processes, which are usually modeled by combining graphical and textual notations. During the business-driven development process, business-process models are taken down to the IT level, where they describe the so-called choreography of services in a Service-Oriented Architecture. The derivation of a service choreography based on a business-process model is simple and straightforward for toy examples only-for realistic applications, many challenges at the methodological and technical level have to be solved. This paper explores these challenges and describes selected solutions that have been developed by the research team of the IBM Zurich Research Laboratory.