Browsing by Author "Härder, Theo"

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Open Access
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.
Open Access
Capturing design dynamics : the CONCORD approach
(1994) Ritter, Norbert; Mitschang, Bernhard; Härder, Theo; Gesmann, Michael; Schöning, Harald
'Computer-Supported Cooperative Work' is a young research area considering applications with strong demands on database technology. Especially design applications need support for cooperation and some means for controlling their inherent dynamics. However, today's CAD systems mostly consisting of a collection of diverse design tools typically do not support these requirements. Therefore, an encompassing processing model is needed that covers the overall design process in general as well as CAD-tool application in particular. As a consequence, this model has to be rich enough to reflect the major characteristics of design processes, e.g., goal-orientation, hierarchical refinement, stepwise improvement as well as team-orientation and cooperation. The CONCORD model that will be described in this paper, reflects the distinct properties of design process dynamics by distinguishing three levels of abstraction. The highest level supports application-specific cooperation control and design process administration, the second considers goal-oriented tool invocation and work-flow management while the third level provides tool processing of design data. To achieve level-spanning control, we rely on transactional facilities provided at the various system layers.
Open Access
Coupling engineering workstations to a database server
(1987) Härder, Theo; Hübel, Christoph; Meyer-Wegener, Klaus; Mitschang, Bernhard
A DBMS kernel architecture is proposed for improved DB support of engineering applications running on a cluster 01 workstations. Using such an approach, part of the DBMS code - an application-specific layer - is allocated close to the corresponding application on a workstation while the kernel code is executed on a central server. Empirical performance results from DB-based engineering applications are reported to justify the chosen DBMS architecture. The paper focuses on design issues of the application layer including server coupling, processing model and application interface. Moreover, a transaction model for long-term database work in a coupled workstation-server environment is investigated in detail.
Open Access
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.
Open Access
Knowledge base management systems - the bases of advanced CAD
(1989) Deßloch, Stefan; Härder, Theo; Mattos, Nelson Mendonca; Mitschang, Bernhard
Semantic expressive representation of design objects, active system behavior combined with reasoning facilities, and efficient implementation concepts are necessary requirements for the construction of better CAD systems. Here, we describe our approach to a knowledge base management system and exemplify its usage for advanced CAD systems.
Open Access
KRISYS : KBMS support for better CAD systems
(1989) Deßloch, Stefan; Härder, Theo; Mattos, Nelson Mendonca; Mitschang, Bernhard
The authors propose a knowledge-base management system based on the integration of database and artificial intelligence technology that provides adequate capabilities for the construction of advanced CAD systems. The approach is evaluated in view of other systems and its suitability is demonstrated by means of some examples from the area of architectural design. Throughout the authors refine their views of advanced CAD and define some inherent characteristics of better CAD.
Open Access
KUNICAD : ein datenbankgestütztes geometrisches Modellierungssystem für Werkstücke
(1987) Härder, Theo; Hübel, Christoph; Langenfeld, Stefan; Mitschang, Bernhard
Es wird ein datenbankgestütztes, volumenorientiertes Modellierungssystem für Werkstücke beschrieben, das als Kernalgorithmus für die geometrische Modellierung ein volumenorientiertes Verfahren einsetzt. Zur Unterstützung der graphischen Repräsentation der Werkstücke werden intern zusätzlich Strukturen nach dem Begrenzungsflächenmodell gehalten, die automatisch aus den CSG-Strukturen abgeleitet und nachgeführt werden. Das KUNICAD-System wird durch seine Gesamtarchitektur, seine Benutzerschnittstelle und sein zugrundeliegendes Anwendermodell skizziert. Die Modellierungskomponente wird durch ihre wesentlichsten Aufgaben - die Darstellung der Objekte und ihre Handhabung - beschrieben. Eine objektunterstützende Datenbankschnittstelle wurde nach dem Zusatzebenen-Architekturkonzept auf der Basis eines CODASYL-Datenbanksystems (UDS) entwickelt. Das implementierte System gestattet das Studium von praxistauglichen CAD-Schnittstellen und erlaubt eine detaillierte Analyse des durch die Datenbankverwaltung bedingten Mehraufwands bei CAD-Operationen.
Open Access
On structuring primitives and communication primitives for design environments
(1992) Ritter, Norbert; Mitschang, Bernhard; Gesmann, Michael; Grasnickel, Andreas; Härder, Theo; Huff, Clarence; Hübel, Christoph; Käfer, Wolfgang; Schöning, Harald; Sutter, Bernd
The evolution of CAD systems can be described in several stages which reflect an increasing effort for system Integration. It starts from a file-and-translator approach evolving to a data-integrated tool environment, and finally reaching the stage of a data-integrated design environment for CAD (sometimes also called CAD Framework). In the following we will detail some aspects of these stages.
Open Access
PRIMA - a database system supporting dynamically defined composite objects
(1992) Gesmann, Michael; Grasnickel, Andreas; Härder, Theo; Hübel, Christoph; Käfer, Wolfgang; Mitschang, Bernhard; Schöning, Harald
PRIMA is a non-standard database system developed at the University Kaiserslautern. Its major purpose is the support of engineering design applications, such as VLSI design and software engineering. The applications require tailored application-dependent interfaces which, however, all share basic notions like that of a composite object. Hence, the approach of PRIMA is to offer an application-independent complex-object interface (the moleculeatom data model, shortly called MAD model) and to provide means to easily augment this interface by application-dependent functionality. In the following, we will concentrate on the MAD model and its implementation.
Open Access
PRIMA : a DBMS prototype supporting engineering applications
(1987) Härder, Theo; Meyer-Wegener, Klaus; Mitschang, Bernhard; Sikeler, Andrea
The design of the Molecule-Atom Data model, aimed at the effective support of engineering applications, is justified and described with its essential properties and features. MAD offers direct and symmetric management of network structures and recursiveness, dynamic object definition and object handling allowing for both vertical and horizontal access. Its prototype implementation PRIMA is discussed using a multi-level model for the DBMS architecture. Our DBMS kernel provides a variety of access path structures, tuning mechanisms, and performance enhancements transparent at the data model interface. PRIMA is assumed to be used in different run-time environments including workstation coupling and multi-processor systems. In particular, it serves as a research vehicle to investigate the exploitation of "semantic parallelism" in single user operations.
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Processing and transaction concepts for cooperation of engineering workstations and a database server
(1988) Härder, Theo; Hübel, Christoph; Meyer-Wegener, Klaus; Mitschang, Bernhard
A DBMS kernel architecture is proposed for improved DB support of engineering applications running on a cluster of workstations. Using such an approach, part of the DBMS code - an application-specific layer - is allocated close to the corresponding application on a workstation while the kernel code is executed on a central server. Emperical performance results from DB-based engineering applications are reported to justify the chosen DBMS architecture. The paper focuses on design issues of the application layer including server coupling, processing model and application interface. Moreover, a transaction model for long-term database work in a coupled workstation-server environment is investigated in detail.
Open Access
Query processing for complex objects
(1992) Härder, Theo; Mitschang, Bernhard; Schöning, Harald
Over the last few years several new data models together with their languages have been developed to meet the increasing requirements of engineering or office applications. A major characteristic of these data models is their ability to process and manage complex objects which the relational model does not provide adequate support for. Whereas the problem of query translation for relational languages has provoked broad research activities during the last fifteen years, the analogous problem of translating non-procedural queries on complex objects into lower level programs for efficient execution has received only little attention. This paper tries to reveal the new aspects of query translation and execution on complex objects as compared to similar activities when processing flat relations. For this purpose, we investigate the essential concepts necessary to perform compilation, optimization, and execution of queries on complex objects.
Open Access
Unterstützung der Ablaufsteuerung in Entwurfsumgebungen durch Versionierung und Konfigurierung
(1994) Ritter, Norbert; Mitschang, Bernhard; Härder, Theo; Nink, Udo
Eine wesentliche Aufgabe von Entwurfsumgebungen besteht in der Integration von einzelnen, eigenständigen Entwurfswerkzeugen sowohl bzgl. einer gemeinsamen Datenhaltung als auch einer gemeinsamen Ablaufsteuerung. Dies erfordert zum einen die integrierte Verwaltung aller Entwurfsdaten sowie die Bereitstellung der für den werkzeugspezifischen Entwurf relevanten Daten. Versionierung und Konfigurierung stellen hierbei die zentralen Konzepte zur umfassenden Beschreibung der Entwurfsdaten dar. Daneben ist auch die Einbindung der einzelnen Werkzeuganwendungen in den Gesamtablauf zu bewerkstelligen. Hierzu wird eine geeignete Entwurfsablaufteuerung benötigt. Ihre Aufgaben bestehen vor allem in der Unterstützung einer kontrollierten Kooperation zwischen zusammenarbeitenden Entwerfern, in der Koordination ggf. vorgeplanter Folgen von Werkzeuganwendungen sowie in der Sicherung einer korrekten Interaktion der Werkzeuge mit der Entwurfsdatenverwaltung. In diesem Artikel beschreiben wir die zentralen Charakteristika der drei grundlegenden Konzepte: Versionierung, Konfigurierung und Ablaufsteuerung. Weiterhin diskutieren wir das Zusammenwirken dieser Konzepte im Rahmen einer Entwurfsumgebung. Dabei kommt deutlich zum Vorschein, daß die Datenbeschreibungsaspekte auf der einen Seite und die Ablaufaspekte auf der anderen Seite sowie deren Zusammenspiel die Eigenschaften einer konkreten Entwurfsumgebung, wie z.B. die Aspekte des parallelen Entwurfs oder die Fehlerbehandlung, entscheidend mitbestimmen.
Open Access
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.
Open Access
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.