Leen Lambers

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.

Conflict detection for graph transformation with negative application conditions

This paper introduces a new theory needed for the purpose of conflict detection for graph transformation with negative application conditions (NACs). Main results are the formulation of a conflict notion for graph transformation with NACs and a conflict characterization derived from it. A critical pair definition is introduced and completeness of the set of all critical pairs is shown. This means that for each conflict, occuring in a graph transformation system with NACs, there exists a critical pair expressing the same conflict in a minimal context. Moreover a necessary and sufficient condition is presented for parallel independence of graph transformation systems with NACs. In order to facilitate the implementation of the critical pair construction for a graph transformation system with NACs a correct construction is formulated. Finally, it is discussed how to continue with the development of conflict detection and analysis techniques in the near future.

A Survey of Triple Graph Grammar Tools

Model transformation plays a central role in Model-Driven Engineer- ing (MDE) and supporting bidirectionality is a current challenge with important applications. Triple Graph Grammars (TGGs) are a formally founded, bidirectional model transformation language shown by numerous case studies to be promising and useful in practice. TGGs have been researched for more than 15 years and multiple TGG tools are under active development. Although a common theoreti- cal foundation is shared, TGG tools differ considerably concerning expressiveness, applicability, efficiency, and the underlying translation algorithm. There currently exists neither a quantitative nor a qualitative overview and comparison of TGG tools and it is quite difficult to understand the different foci and corresponding strengths and weaknesses. Our contribution in this paper is to develop a set of criteria for com- paring TGG tools and to provide a concrete quantitative and qualitative comparison of three TGG tools.

Behavior Preservation in Model Refactoring Using DPO Transformations with Borrowed Contexts

Behavior preservation, namely the fact that the behavior of a model is not altered by the transformations, is a crucial property in refactoring. The most common approaches to behavior preservation rely basically on checking given models and their refactored versions. In this paper we introduce a more general technique for checking behavior preservation of refactorings defined by graph transformation rules. We use double pushout (DPO) rewriting with borrowed contexts, and, exploiting the fact that observational equivalence is a congruence, we show how to check refactoring rules for behavior preservation. When rules are behavior-preserving, their application will never change behavior, i.e., every model and its refactored version will have the same behavior. However, often there are refactoring rules describing intermediate steps of the transformation, which are not behavior-preserving, although the full refactoring does preserve the behavior. For these cases we present a procedure to combine refactoring rules to behavior-preserving concurrent productions in order to ensure behavior preservation. An example of refactoring for finite automata is given to illustrate the theory.

Towards a model transformation intent catalog

We report on our ongoing effort to build a catalog of model transformation intents that describes common uses of model transformations in Model-Driven Engineering (MDE) and the properties they must or may possess. We present a preliminary list of intents and common properties. One intent (transformation for analysis) is described in more detail and the description is used to identify transformations with the same intent in a case study on the use of MDE techniques for the development of control software for a power window.

Symbolic Attributed Graphs for Attributed Graph Transformation

In this paper we present a new approach to deal with attributed graphs and attributed graph transformation. This approach is based on working with what we call symbolic graphs, which are graphs labelled with variables together with a formula that constrains the possible values that we may assign to these variables. In particular, in this paper we will compare in detail this new approach with the standard approach to attributed graph transformation.

M-Adhesive Transformation Systems with Nested Application Conditions. Part 2: Embedding, Critical Pairs and Local Confluence

Graph transformation systems have been studied extensively and applied to several areas of computer science like formal language theory, the modeling of databases, concurrent or distributed systems, and visual, logical, and functional programming. In most kinds of applications it is necessary to have the possibility of restricting the applicability of rules. This is usually done by means of application conditions. In this paper, we continue the work of extending the fundamental theory of graph transformation to the case where rules may use arbitrary (nested) application conditions. More precisely, we generalize the Embedding theorem, and we study how local confluence can be checked in this context. In particular, we define a new notion of critical pair which allows us to formulate and prove a Local Confluence Theorem for the general case of rules with nested application conditions. All our results are presented, not for a specific class of graphs, but for any arbitrary M-adhesive category, which means that our results apply to most kinds of graphical structures. We demonstrate our theory on the modeling of an elevator control by a typed graph transformation system with positive and negative application conditions.

Efficient Detection of Conflicts in Graph-based Model Transformation

Using graph transformation as a formalism to specify model transformation, termination and confluence of the graph transformation system are often required properties. Only under these two conditions, existence and uniqueness of the outcoming model is ensured. Verifying confluence of a graph transformation system can be reduced to checking both local confluence and termination. A graph transformation system is locally confluent, if all its conflicts in a minimal context can be resolved. Formally, this means, that all critical pairs of the graph transformation system should be strictly confluent. Thus, answering the question of local confluence of a graph transformation system, requires the following two steps. At first the computation of all critical pairs is necessary. Secondly this set of critical pairs has to be tested for strict confluence. This paper concentrates on the first step, proposing an efficient method to compute the set of all critical pairs of a given graph transformation system. Efficiency is obtained because of the following two main reasons. At first all pairs of rules are analyzed to check if they can actually cause a conflict. Then for each conflict inducing pair of rules, the set of critical pairs is computed in a constructive way, avoiding needless computations. The overall goal of this paper is to encourage tool development and enhancement concerning the detection of conflicts in a graph transformation system. It should be an aid to translate the main theoretical results concerning confluence of a graph transformation system into practical methods for the analysis of model transformations specified with graph transformation.

Bridging the gap between formal semantics and implementation of triple graph grammars

The correctness of model transformations is a crucial element for model-driven engineering of high-quality software. A prerequisite to verify model transformations at the level of the model transformation specification is that an unambiguous formal semantics exists and that the implementation of the model transformation language adheres to this semantics. However, for existing relational model transformation approaches, it is usually not really clear under which constraints particular implementations really conform to the formal semantics. In this paper, we will bridge this gap for the formal semantics of triple graph grammars (TGG) and an existing efficient implementation. While the formal semantics assumes backtracking and ignores non-determinism, practical implementations do not support backtracking, require rule sets that ensure determinism, and include further optimizations. Therefore, we capture how the considered TGG implementation realizes the transformation by means of operational rules, define required criteria, and show conformance to the formal semantics if these criteria are fulfilled. We further outline how static and runtime checks can be employed to guarantee these criteria.

M-adhesive transformation systems with nested application conditions. Part 1: parallelism, concurrency and amalgamation

Nested application conditions generalise the well-known negative application conditions and are important for several application domains. In this paper, we present Local Church-Rosser, Parallelism, Concurrency and Amalgamation Theorems for rules with nested application conditions in the framework of M-adhesive categories, where M-adhesive categories are slightly more general than weak adhesive high-level replacement categories. Most of the proofs are based on the corresponding statements for rules without application conditions and two shift lemmas stating that nested application conditions can be shifted over morphisms and rules.