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Publication Type: search.filters.UBSTyp.KonferenzbeitragAuthor: search.filters.author.Mitschang, Bernhard

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Now showing 1 - 10 of 27
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    SQL/XNF - processing composite objects as abstractions over relational data
    (1993) Mitschang, Bernhard; Pirahesh, Hamid; Pistor, Peter; Lindsay, Bruce; Südkamp, Norbert
    An extension to SQL, called the SQL extended normal form (XNF), is discussed. It enhances relational technology by a composite object facility, which comprises not only extraction of composite objects from existing databases but also efficient navigation and manipulation facilities provided by an appropriate application programming interface. The language itself allows sharing of the database among normal form SQL applications and composite object applications. It provides proper subsetting of the database and subsequent structuring, exploiting subobject sharing and recursion, all based on its powerful composite object constructor concept, which is closed under the language operations. XNF is integrated into the relational framework, thus benefiting from the available technology such as relational engine and query optimization.
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    Extending the relational algebra to capture complex objects
    (1989) Mitschang, Bernhard
    An important direction in database research for non-standard applications (e.g. engineering or design applications) deals with adequate support for complex objects. Without doubt, the provision of network structures and shared subobjects as well as support for dynamic object definition and appropriate manipulation facilities is urgently needed for natural and accurate modeling as well as for efficient processing of the applications' objects. These concepts are the major concern of the molecule-atom data model (MAD model) and its molecule algebra which is introduced in this paper. They make the model stand out compared to the relational model and even to models limited to hierarchical and statically defined complex objects. By means of the molecule algebra a precise and complete specification of one conceivable kind of complex object processing and its inherent semantics is provided. Furthermore, this algebra is used as a sound basis to express the semantics of the high level query language MOL (molecule query language) that is able to deal with complex objects in a descriptive manner.
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    Information structures and database support for solid modeling
    (1989) Härder, Theo; Hübel, Christoph; Mitschang, Bernhard
    The question we are going to investigate is how to map solid representations to DB structures and how to process this information efficiently. Starting from analytical representations based on analytical methods we discuss the use of constructive solid geometry and boundary representation models with various refinements. Furthermore, additional submodels (organizational, technological, physical) are considered in order to obtain an overall product model. This model representing all important aspects of a complex design object may serve to derive special object representations needed by existing engineering tools or by mathematical methods (e.g. finite elements). Today's DBMS are unable to meet the increasing requirements of engineering applications that would prefer to use a DBMS. To alter this situation, a new generation of DBMS architectures tailored to the demands of such enhanced applications have to be developed. As a consequence, the flexibility and expressiveness of data models as well as the handling of application objects must be greatly improved before interactive design work can be supported. We outline our data model concepts and architectural decisions to provide effective data management support. Our DBMS architecture consists of a neutral kernel part running on a server machine and an application layer tailored to solid modeling tasks which together with the application, i.e. the solid modeler is allocated to the workstation.
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    Using PRIMA-DBMS as a testbed for parallel complex-object processing
    (1992) Hübel, Christoph; Mitschang, Bernhard; Gesmann, Michael; Grasnickel, Andreas; Käfer, Wolfgang; Schöning, Harald; Härder, Theo
    The PRIMA-DBMS approach is explained by introducing PRIMA's architecture and query processing framework. The PRIMA-DBMS constitutes a testbed that is flexible enough to support evaluation and validation of quite a variation of different strategies for complex-object processing taking into account different parallelization levels and different hardware environments. Thus, PRIMA marks an important step towards our main research goal concerning measures for efficient complex-object processing: the measures that are in competition with each other are query optimization, query evaluation strategies, and massive storage, that all benefit from parallelism. The programming environment that supports the parallel DBMS processing is introduced with special emphasis on its ability for parametrization and configuration. A case study of the PRIMA testbed illustrates our first investigations and demonstrates a methodology for evaluation and tuning of PRIMA configurations.
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    Abbildung von Frames auf neuere Datenmodelle
    (1987) Härder, Theo; Mattos, Nelson Mendonca; Mitschang, Bernhard
    Es wird die Abbildung von Frames mit ihren Modellierungskonzepten und charakteristischen Operationen auf objektorientierte Datenmodelle untersucht, um Wissensrepräsentation in sogenannten Non-Standard-Datenbanksystemen - beispielsweise für Expertensystem-Anwendungen - unterstützen zu können. Nach einem Vergleich der Eigenschaften von Relationenmodell, NF 2-Modell und MAD-Modell für diese Aufgabe wird eine Bewertung der verschiedenen Ansätze vorgenommen, um ihre Tauglichkeit für die Frame-Modellierung deutlicher herauszukristallisieren.
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    Flexible Entwurfsdatenverwaltung für CAD-Frameworks : Konzept, Realisierung und Bewertung
    (1993) Käfer, Wolfgang; Mitschang, Bernhard
    Eine der Hauptzielrichtungen von CAD-Frameworks ist die Integration von einzelnen, eigenständigen CAD-Werkzeugen mittels einer zentralen Datenverwaltung. Wesentliche Aufgaben hierbei sind die Verwaltung aller entwurfsrelevanten Daten sowie die effiziente Bereitstellung werkzeugrelevanter Daten für den werkzeugspezifischen Entwurfsschritt. Hierzu sind die vom jeweiligen Werkzeug zu bearbeitenden Entwurfsdaten bzw. Entwurfsobjekte zu selektieren und in der jeweils benötigten Form bereitzustellen. Nach Beendigung des Entwufsschrittes sind die geänderten Daten in den aktuellen Datenbestand zu integrieren. Um diese schwierige Aufgabe meistern zu können, ist es nötig, die vorherrschenden Objekt- und Entwurfsstrukturen entsprechend zu berücksichtigen. Das hier vorgestellte Objekt-Versions-Modell OVM soll diesen hohen Anforderungen entsprechen. Mit OVM werden (versionierte) Objekte aus Elementarobjekten zusammengesetzt; zwischen diesen Objekten können Objekt-, Versions-, und Konfigurationsbeziehungen in flexibler Art und Weise aufgebaut werden. Die zugehörige Manipulationssprache OML erlaubt ein adäquates Arbeiten mit den so strukturierten Objekten. OVM bietet eine hohe Abstraktion von der zugrundeliegenden Datenrepräsentation, so daß eine OVM-Realisierung im Prinzip mit unterschiedlichen DBS durchgeführt werden kann. Unsere OVM-Realisierung mittels des PRIMA-Systems wird vorgestellt, die gewonnenen Erfahrungen berichtet und eine vergleichende Bewertung zu Realisierungsalternativen gegeben.
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    Towards effective support of engineering information systems
    (1988) Hübel, Christoph; Mitschang, Bernhard
    Existing interfaces to nowadays database systems show to be increasingly unsuitable for the evolving wide spectrum of engineering applications (e.g. CAD/CAM, geographic information management, knowledge-based systems for planning and design, etc.). This is further intensified due to the workstation-oriented processing scheme prevailing in the engineering area. Starting with an architectural approach tailored to this distributed processing concept, we propose the PRIMA-NDBS and its most important interfaces, i.e. the data model and the application/user interface offering effective support of engineering information systems.
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    Use of inherent parallelism in database operations
    (1986) Härder, Theo; Hübel, Christoph; Mitschang, Bernhard
    Non-standard applications of database systems (e.g. CAD) are characterized by complex objects and powerful user operations. Units of work decomposed from a single user operation are said to allow for inherent semantic parallelism when they do not conflict with each other at the level of decomposition. Hence, they can be scheduled concurrently. In order to support this processing scheme it is necessary to organize parallel execution by adequate control units. Therefore, client-server processes and nested transactions are applied to hierarchically structure the DBS-operations. On the other hand, the DBS-code itself has to be mapped onto a multiprocessor system to take advantage of multiple processing units.
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    Composite-object views in relational DBMS: an implementation perspective : (extended abstract)
    (1994) Pirahesh, Hamid; Mitschang, Bernhard; Südkamp, Norbert; Lindsay, Bruce
    We present a novel approach for supporting Composite Objects (CO) as an abstraction over the relational data. This approach brings the advanced CO model to existing relational databases and applications, without requiring an expensive migration to other DBMSs which support CO. The concept of views in relational DBMSs (RDBMS) gives the basis for providing the CO abstraction. This model is strictly an extension to the relational model, and it is fully upward compatible with it. We present an overview of the data model. We put emphasis in this paper on showing how we have made the extensions to the architecture and implementation of an RDBMS (Starburst) to support this model. We show that such a major extension to the data model is in fact quite attractive both in terms of implementation cost and query performance. We introduce a CO cache for efficient navigation through components of a CO. Our work on CO enables existing RDBMSs to incorporate efficient CO facilities at a low cost and at a high degree of application reusability and database sharability.
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    MAD : ein Datenmodell für den Kern eines Non-Standard-Datenbanksystems
    (1987) Mitschang, Bernhard
    Eine zentrale Anforderung an Datenbanksysteme für den Einsatz in den sog. nichtkonventionellen Anwendungen besteht in der anwendungsgerechten Modellierung und Verwaltung der Anwendungsobjekte. Von dem Architekturkonzept der DBS-Kern-Architektur ausgehend, werden zum einen Anforderungen an die Datenmodelle der DBS-Kern-Schnittstelle erarbeitet und zum anderen verschiedene Datenmodelle diesbezüglich analysiert. Dieser Kriterienkatalog und die (teilweise) Unzulänglichkeit der untersuchten Datenmodelle gaben den Anlaß zur Entwicklung des Molekül-Atom-Datenmodells (MAD-Modell). Hier werden nun sowohl die Modellierungs- als auch die Verarbeitungskonzepte des MAD-Modells herausgearbeitet und beispielhaft vorgestellt. Weiterhin werden die Konzepte einer SQL-ähnlichen Sprache angegeben, die das MAD-Modell an der DBS-Kern-Schnittstelle zur Verfügung stellt.