The W3C OWL 2 recommendation is an ontology language for the Semantic Web. It allows defining both schema (i.e., entities, axioms, and expressions) and instances (i.e., individuals) of ontologies. However, OWL 2 lacks explicit support for time-varying schema or for time-varying instances. Hence, knowledge engineers or maintainers of semantics-based Web resources have to use ad hoc techniques to specify OWL 2 time-varying ontologies. In this paper, for a disciplined and systematic approach to the temporal management of Semantic Web ontologies, we propose the adoption of a framework called temporal OWL 2 (τOWL), which is inspired by the τXSchema framework defined for XML data. In a way similar to what happens in τXSchema, τOWL allows creating a temporal OWL 2 ontology from a conventional (i.e., non-temporal) OWL 2 ontology and a set of logical and physical annotations. Logical annotations identify which elements of the ontology can vary over time; physical annotations specify how the time-varying aspects are represented in the OWL 2 document. Using annotations to integrate temporal aspects in the traditional Semantic Web, our framework (1) guarantees logical and physical data independence for temporal schemas and (2) provides a low-impact solution, since it requires neither modifications of existing Semantic B Zouhaier Brahmia Web ontologies, nor extensions to the OWL 2 recommendation and Semantic Web standards. Moreover, since the conventional schema and annotation documents could evolve over time to respond to new applications' requirements, τOWL supports temporal schema versioning by allowing changing these components and by keeping track of their evolution through the conventional schema versions and annotation document versions, respectively. Two complete sets of operations are proposed for changing the conventional schema and annotation documents; to complete the figure, a set of operations is also introduced for updating temporal schema which must be changed consequently each time one of the mentioned components evolves over time. To show the feasibility of our approach, a prototype tool, named τOWL-Manager, is presented.

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Like other components of Semantic Web-based applications, ontologies are evolving over time to reflect changes in the real world. Several of these applications require keeping a full-fledged history of ontology changes so that both ontology instance versions and their corresponding ontology schema versions are maintained. Updates to an ontology instance could be non-conservative that is leading to a new ontology instance version no longer conforming to the current ontology schema version. If, for some reasons, a non-conservative update has to be executed, in spite of its consequence, it requires the production of a new ontology schema version to which the new ontology instance version is conformant so that the new ontology version produced by the update is globally consistent. In this paper, we first propose an approach that supports ontology schema changes which are triggered by non-conservative updates to ontology instances and, thus, gives rise to an ontology schema versioning driven by instance updates. Note that in an engineering perspective, such an approach can be used as an incremental ontology construction method driven by the modification of instance data, whose exact structure may not be completely known at the initial design time. After that, we apply our proposal to the already established [Formula: see text]OWL (Temporal OWL 2) framework, which allows defining and evolving temporal OWL 2 ontologies in an environment that supports temporal versioning of both ontology instances and ontology schemas, by extending it to also support the management of non-conservative updates to ontology instance versions. Last, we show the feasibility of our approach by dealing with its implementation within a new release of the [Formula: see text] OWL-Manager tool.

High performance computing is one of the most exciting technologies used in solving real-world problems in computational science and engineering. It is expected that the years to come will witness a proliferation of the use of parallel and distributed systems. High performance computing plays an important role in determining and shaping research and development activities in numerous academic and industrial branches, especially when the solution of large-scale problems must cope with ever-increasingly harder requirements for computing time and storage space. This special workshop is an international forum that brings together researchers, practitioners, and students working in the areas of computer architecture, system and network, algorithms, and applications to present, discuss, and exchange ideas, results, work in progress, and experience of research and practice in the area of high performance computing for science and engineering applications.The workshop received many submissions representing 7 countries. All submissions were carefully reviewed by our committee members and external reviewers. In order to allocate as many papers as possible and also keep the high quality of the workshop, we finally decided to accept 14 papers for oral technical presentation at the workshop. We believe these papers and their presentation will provide novel ideas and the state-of-the-art techniques as well as stimulate future research activities in the area of high performance computing for science and engineering applications.The program for this workshop is the result of hard and excellent work of many people, including the authors, the external reviewers, and the program committee members. We would like to express our sincere appreciation to all of them for their cooperation in completing the workshop program under a tight schedule. We also want to thank Fusun Ozguner and Tim Pinkston, ICPP-2006 Workshop Co-Chairs, for encouraging and helping the inclusion of HPSEC-06 in ICPP-06.

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