Claudia Ermel

Information preserving bidirectional model transformations

Within model-driven software development, model transformation has become a key activity. It refers to a variety of operations modifying a model for various purposes such as analysis, optimization, and code generation. Most of these transformations need to be bidirectional to e.g. report analysis results, or keep coherence between models. In several application-oriented papers it has been shown that triple graph grammars are a promising approach to bidirectional model transformations. But up to now, there is no formal result showing under which condition corresponding forward and backward transformations are inverse to each other in the sense of information preservation. This problem is solved in this paper based on general results for the theory of algebraic graph transformations. The results are illustrated by a transformation of class models to relational data base models which has become a quasi-standard example for model transformation.

Precise Semantics of EMF Model Transformations by Graph Transformation

Model transformation is one of the key activities in model-driven software development. An increasingly popular technology to define modeling languages is provided by the Eclipse Modeling Framework (EMF). Several EMF model transformation approaches have been developed, focusing on different transformation aspects. To validate model transformations wrt. functional behavior and correctness, a formal foundation is needed. In this paper, we define EMF model transformations as a special kind of typed graph transformations using node type inheritance. Containment constraints of EMF model transformations are translated to a special kind of EMF model transformation rules such that their application leads to consistent transformation results only. Thus, we identify a kind of EMF model transformations which behave like algebraic graph transformations. As a consequence, the rich theory of algebraic graph transformation can be applied to these EMF model transformations to show functional behavior and correctness. We illustrate our approach by selected refactorings of simplified statechart models.

Generation of visual editors as eclipse plug-ins

Visual Languages (VLs) play an important role in software system development. Especially when looking at well-defined domains, a broad variety of domain specific visual languages are used for the development of new applications. These languages are typically developed specifically for a certain domain in a way that domain concepts occur as primitives in the language alphabet. Visual modeling environments are needed to support rapid development of domain-specific solutions.In this contribution we present a general approach for defining visual languages and for generating language-specific tool environments. The visual language definition is again given in a visual manner and precise enough to completely generate the visual environment. The underlying technology is Eclipse with its plug-in capabilities on the one hand, and formal graph transformation techniques on the other hand. More precisely, we present an Eclipse plug-in generating Java code for visual modeling plug-ins which can be directly executed in the Eclipse Runtime-Workbench.

On-the-Fly Construction, Correctness and Completeness of Model Transformations Based on Triple Graph Grammars

Triple graph grammars (TGGs) are a formal and intuitive concept for the specification of model transformations. Their main advantage is an automatic derivation of operational rules for bidirectional model transformations, which simplifies specification and enhances usability as well as consistency. In this paper we continue previous work on the formal definition of model transformations based on triple graph rules with negative application conditions (NACs). The new notion of partial source consistency enables us to construct consistent model transformations on-the-fly instead of analyzing consistency of completed model transformations. We show the crucial properties termination, correctness and completeness (including NAC-consistency) for the model transformations resulting from our construction. Moreover, we define parallel independence for model transformation steps which allows us to perform partial-order reduction in order to improve efficiency. The results are applicable to several relevant model transformations and in particular to our example transformation from class diagrams to database models.

Rule-based refinement of high-level nets preserving safety properties

The concept of rule-based modification developed in the area of algebraic graph transformations and high-level replacement systems has recently shown to be a powerful concept for vertical stucturing of Petri nets. This includes low-level and high-level Petri nets, especially algebraic high-level nets which can be considered as an integration of algebraic specifications and Petri nets. In a large case study rule-based modification of algebraic high-level nets has been applied successfully for the requirements analysis of a medical information system. The main new result in this paper extends rule-based modification of algebraic highlevel nets such that it preserves safety properties formulated in terms of temporal logic. For software development based on rule-based modification of algebraic high-level nets as a vertical development strategy this extension is an important new technique. It is called rule-based refinement. As a running example an important safety property of a medical information system is considered and is shown to be preserved under rule-based refinement.

A fundamental approach to model versioning based on graph modifications: from theory to implementation

In model-driven engineering, models are primary artifacts that can evolve heavily during their life cycle. Therefore, versioning of models is a key technique to be offered by integrated development environments for model-driven engineering. In contrast to text-based versioning systems, we present an approach that takes model structures and their changes over time into account. Considering model structures as graphs, we define a fundamental approach where model revisions are considered as graph modifications consisting of delete and insert actions. Two different kinds of conflict detection are presented: (1) the check for operation-based conflicts between different graph modifications, and (2) the check for state-based conflicts on merged graph modifications. For the merging of graph modifications, a two-phase approach is proposed: First, operational conflicts are temporarily resolved by always giving insertion priority over deletion to keep as much information as possible. Thereafter, this tentative merge result is the basis for manual conflict resolution as well as for the application of repair actions that resolve state-based conflicts. If preferred by the user, giving deletion priority over insertion might be one solution. The fundamental concepts are illustrated by versioning scenarios for simplified statecharts. Furthermore, we show an implementation of this fundamental approach to model versioning based on the Eclipse Modeling Framework as technical space.

Semantical Correctness and Completeness of Model Transformations Using Graph and Rule Transformation

An important requirement of model transformations is the preservation of the behavior of the original model. A model transformation is semantically correctif for each simulation run of the source system we find a corresponding simulation run in the target system. Analogously, we have semantical completeness, if for each simulation run of the target system we find a corresponding simulation run in the source system. In our framework of graph transformation, models are given by graphs, and graph transformation rules are used to define the operational behavior of visual models (called simulation rules). In order to compare the semantics of source and target models, we assume that in both cases operational behavior can be defined by simulation rules. The model transformation from source to target models is given by another set of graph transformation rules. These rules are also applied to the simulation rules of the source model. The main result in this paper states the conditions for model and rule transformations to be semantically correct and complete. The result is applied to analyze the behavior of a model transformation from a domain-specific visual language for production systems to Petri nets.

Formal foundation of consistent EMF model transformations by algebraic graph transformation

Model transformation is one of the key activities in model-driven software development. An increasingly popular technology to define modeling languages is provided by the Eclipse Modeling Framework (EMF). Several EMF model transformation approaches have been developed, focusing on different transformation aspects. To validate model transformations with respect to functional behavior and correctness, a formal foundation is needed. In this paper, we define consistent EMF model transformations as a restricted class of typed graph transformations using node type inheritance. Containment constraints of EMF model transformations are translated to a special kind of graph transformation rules such that their application leads to consistent transformation results only. Thus, consistent EMF model transformations behave like algebraic graph transformations and the rich theory of algebraic graph transformation can be applied to these EMF model transformations to show functional behavior and correctness. Furthermore, we propose parallel graph transformation as a suitable framework for modeling EMF model transformations with multi-object structures. Rules extended by multi-object structures can specify a flexible number of recurring structures. The actual number of recurring structures is dependent on the application context of such a rule. We illustrate our approach by selected refactorings of simplified statechart models. Finally, we discuss the implementation of our concepts in a tool environment for EMF model transformations.

Formal analysis and verification of self-healing systems

Self-healing (SH-)systems are characterized by an automatic discovery of system failures, and techniques how to recover from these situations. In this paper, we show how to model SH-systems using algebraic graph transformation. These systems are modeled as typed graph grammars enriched with graph constraints. This allows not only for formal modeling of consistency and operational properties, but also for their analysis and verification using the tool AGG. We present sufficient static conditions for self-healing properties, deadlock-freeness and liveness of SH-systems. The overall approach is applied to a traffic light system case study, where the corresponding properties are verified.

On the relationship of model transformations based on triple and plain graph grammars

Triple graph grammars have been applied and implemented as a formal basis for model transformations in a variety of application areas. They convince by special abilities in automatic derivation of forward, backward and several other transformations out of just one specified set of rules for the integrated model defined by a triple of graphs. While many case studies and all implementations, which state that they are using triple graph grammars, do not use triples of graphs, this paper presents the justification for many of them. It shows a one to one correspondence between triple graph grammars and suitable plain graph grammars, thus results and benefits of the triple case can be transferred to the plain case. Main results show the relationship between both graph transformation approaches, syntactical correctness of model transformations based on triple graph grammars and a sound and complete condition for functional behaviour. Theoretical results are elaborated on an intuitive case study for a model transformation from class diagrams to database models.