Andy Schürr

Specification of Graph Translators with Triple Graph Grammars

Data integration is a key issue for any integrated set of software tools. A typical CASE environment, for instance, offers tools for the manipulation of requirements and software design documents, and it provides more or less sophisticated assistance for keeping these documents in a consistent state. Up to now, almost all data consistency observing or preserving integration tools are hand-crafted due to the lack of generic implementation frameworks and the absence of adequate specification formalisms. Triple graph grammars are intended to fill this gap and to support the specification of interdependencies between graph-like data structures on a very high level. Furthermore, they are the fundamentals of a new machinery for the production of batch-oriented as well as incrementally working data integration tools.

GXL: toward a standard exchange format

This paper describes ongoing work toward the development of a standard software exchange format (SEF), for exchanging information among tools that analyze computer programs. A particular exchange format called GXL (Graph Exchange Language) is proposed. GXL can be viewed as a merger of well known formats (e.g. GraX, PROGRES, RPA, RSF and TA) for exchanging typed, attributed, directed graphs. By using XML as the notation, GXL offers a scalable and adaptable means to facilitate interoperability of reengineering tools.

Bidirectional Transformations: A Cross-Discipline Perspective

The GRACE International Meeting on Bidirectional Transformations was held in December 2008 near Tokyo, Japan. The meeting brought together researchers and practitioners from a variety of sub-disciplines of computer science to share research efforts and help create a new community. In this report, we survey the state of the art and summarize the technical presentations delivered at the meeting. We also describe some insights gathered from our discussions and introduce a new effort to establish a benchmark for bidirectional transformations.

Graph transformation for specification and programming

The framework of graph transformation combines the potentials and advantages of both, graphs and rules, to a single computational paradigm. In this paper we present some recent developments in applying graph transformation as a rule-based framework for the specification and development of systems, languages, and tools. After reviewing the basic features of graph transformation, we discuss a selection of applications, including the evaluation of functional expressions, the specification of an interactive graphical tool, an example specification for abstract data types, and the definition of a visual database query language. The case studies indicate the need for suitable structuring principles which are independent of a particular graph transformation approach. To this end, we present the concept of a transformation unit, which allows systematic and structured specification and programming based on graph transformation.

15 Years of Triple Graph Grammars

Triple graph grammars (TGGs) have been invented 15 years ago as a formalism for the declarative specification of bidirectional graph-to-graph translations. In this paper we present a list of still open problems concerning the interpretation and the expressiveness of TGGs. We will comment on extensions proposed to improve the original approach and the drawbacks that arise thereof. Consequently a more precise formalization of compulsory properties of the translation of triple graph grammars into forward and backward graph translation functions is given. Regarding these properties an interpretation and implementation of negative application conditions is derived that does not destroy the benefits of the original approach. Additionally a new demand-driven forward/backward translation rule application strategy is proposed. It guarantees for the first time automatically a correct ordering of rule applications without imposing any additional requirements on the structure of the regarded graphs.

Graph Grammar Engineering with PROGRES

Graph-like data structures and rule-based systems play an important role within many branches of computer science. Nevertheless, their symbiosis in the form of graph rewriting systems or graph grammars are not yet popular among software engineers. This is a consequence of the fact that graph grammar tools were not available until recently and of the lack of knowledge about how to use graph grammars for software development purposes. “Graph grammar engineering” is a first attempt to establish a new graph and rule centered methodology for the development of information system components. Having its roots in the late 80s it gradually evolved from a “paper and pencil” specification formalism to a tool-assisted specification and rapid prototyping approach.

MOFLON: a standard-compliant metamodeling framework with graph transformations

The crucial point in Model Driven Architecture (MDA) is that software and system development are based on abstract models that are successively transformed into more specific models, ideally resulting in the desired system. To this end, developers must be enabled to model different aspects like structure, behavior, consistency constraints of the system. This results in a variety of related models, which in turn need tool support on the metalevel. However, there is a lack of tools offering uniform support for metamodel definition, analysis, transformation, and integration. In this paper we present the metamodeling framework MOFLON that addresses these issues by bringing together the latest OMG standards with graph transformations and their formal semantics. MOFLON provides a combination of visual and textual notations and offers powerful modularization concepts. Using MOFLON, developers can generate code for specific tools needed to perform the desired modeling tasks.

Benchmarking for graph transformation

Model transformation (MT) is a key technology in the model-driven development approach of software engineering that provides automated means to capture the evolution of models and mappings between modeling languages. The pattern and rule-based paradigm of graph transformation is considered a very popular approach for specifying such model transformations. While the expressiveness of different MT specification techniques is frequently compared on well-known transformation problems (e.g. UML-to-XMI, or UML-to-EJB mappings), no such benchmarks exist currently for comparing the performance of different model transformation tools. In the paper, we propose a systematic method for quantitative benchmarking in order to assess the performance of graph transformation tools. Typical features of the graph transformation paradigm and various optimization strategies exploited in different toots are identified and categorized. Moreover, the performance of several popular graph transformation tools is measured and compared on a well-known distributed mutual exclusion problem.

Efficient parsing of visual languages based on critical pair analysis and contextual layered graph transformation

The paper proposes an extension of layered graph grammars (LGGs), which have been introduced for the definition of visual languages (VLs). Offering new constructs like negative application conditions (NACs) it allows one to produce more concise VL definitions. A new layering condition and critical pair analysis are the prerequisites for a new parsing algorithm which avoids the exponential behaviour of LGGs in many cases.

GXL: a graph-based standard exchange format for reengineering

GXL (Graph eXchange Language) is an XML-based standard exchange format for sharing data between tools. Formally, GXL represents typed, attributed, directed, ordered graphs which are extended to represent hypergraphs and hierarchical graphs. This flexible data model can be used for object-relational data and a wide variety of graphs. An advantage of GXL is that it can be used to exchange instance graphs together with their corresponding schema information in a uniform format, i.e. using a common document type specification. This paper describes GXL and shows how GXL is used to provide interoperability of graph-based tools. GXL has been ratified by reengineering and graph transformation research communities and is being considered for adoption by other communities.