The conception of an ontology is a complex task influenced by numerous factors like the point of view of the authors or the level of details. Consequently, several ontologies have been developed to model identical or related domains leading to partially overlapping representations. This divergence of conceptualization requires the study of ontologies merging in order to create a common reposito...

Graph rewriting is a powerful technique that requires graph pattern matching, which is an NP-complete problem. We present GrGen, a generative programming system for graph rewriting, which applies heuristic optimizations. According to Varró’s benchmark it is at least one order of magnitude faster than any other tool known to us. Our graph rewriting tool implements the well-founded single-pushout...

As presented in Ehrig et al. (Fundamentals of Algebraic Graph Transformation, EATCS Monographs, Springer, 2006), adhesive high-level replacement (HLR) categories and systems are an adequate framework for several kinds of transformation systems based on the double pushout approach. Since (weak) adhesive HLR categories are closed under product, slice, coslice, comma and functor category construct...

Some of the problems of using refinement alone in the construction of specifications from simple abstract models is used as the spur for the introduction of retrenchment, a method based on the main ideas of refinement, but one which is more liberal in character. The basics of the retrenchment mechanism are presented. The paper then examines one particular way in which a retrenchment and a refin...

Categories in which cocones satisfy certain exactness conditions w.r.t. pullbacks are subject to current research activities in theoretical computer science. Usually, exactness is expressed in terms of properties of the pullback functor associated with the cocone. Even in the case of non-exactness, researchers in model semantics and rewriting theory inquire an elementary characterization of the...

Introduction 150 Organization 152 Acknowledgments 152 1. Symmetric spectra 153 1.1. Simplicial sets 153 1.2. Symmetric spectra 154 1.3. Simplicial structure on Sp 156 1.4. Symmetric Ω-spectra 158 2. The smash product of symmetric spectra 159 2.1. Symmetric sequences 159 2.2. Symmetric spectra 162 2.3. The ordinary category of spectra 165 3. Stable homotopy theory of symmetric spectra 165 3.1. S...

Meta-typing, as for example employed in the Progres environment , is syntactic sugar making the speciication of typed graph grammar systems more convenient. This paper presents an approach of meta-typing that ts in the well-elaborated framework of the typed single pushout (spo) approach to graph transformation. In a rst step the node meta-typing system of Progres is generalized such that edges ...

The advent of the WWW has led to an abundance of information which is distributed on numerous Web sites of heterogeneous structure and coverage. It is therefore important to extract, combine and restructure these distributed data in order to facilitate the access to it. The HyperView methodology models Web sites and their HTML pages as graphs from which information is extracted by a hierarchy o...