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Research Focus

The department Applications of Parallel and Distributed Systems has its "traditional" field of work in the complex areas of database and information systems. A multitude of system and application projects has been carried out, constantly exploring new subject areas. The emphasis of the department's research are the following:

Databases and Transaction Management for Open Systems

In this research area we are determining how database management systems and their functionality can be used in open systems that do not comprise central administration components. The WWW (or the Intra-/Internet in general) might be seen as a typical example of such systems, but similar approaches including mobile access and processing facilities are also considered (e.g. OMG and OSF proposals). Evaluation of concepts is done by specific prototypes and related example applications like earth observations systems (EOS) or product data management (PDM).

Parallel Database Technology

New application areas with more demanding requirements or databases within open networks of information systems lead to a rapid increase of data volumes and query complexity. Well-known examples are the areas OLAP and data mining, profiling services or publish/subscribe services. The necessity to process large data sets very efficiently and to reduce response times requires parallel database technology. However, whenever possible, this should be transparent to the user. Parallelization steps which are considered in department projects are above all input/output, operators of the database engine, and measures to parallelize query execution plans.

Extensible database technology

The first commercial object-relational DBMS are available since some years. This technology promises to manage complex data structures with an efficient support for complex queries at the same time. Furthermore, DBMS vendors enable third party vendors to extend the base systems by program packages which are specific for an application area. These packages contain new data structures together with corresponding operators, support for more efficient query processing and meta data. An example is a package that adds support for geographic information systems by providing base functionality like geometric data structures, systems of coordinates, and spatial queries, for example. Further application areas like data mining and profiling are examined within this technology framework.

Query Processing in Database Systems

Today`s database systems are used in many diverse application areas (e.g. business and administration, engineering or knowledge-based applications) for efficient data management. The requirements for database processing and especially for query processing are mainly determined by prevailing development trends like e.g. extension of data models, use of multi-processor or multi-computer architectures for database servers or workstation/server environments. In this project area we develop conceptual and implementory foundations for advanced query processing. Furthermore we examine technologies that form a reusable and extensible base to built adapted query processors. These concepts allow to customize query processing engines to specific application scenarios. Obvious advantages of this approach are a substantially reduced development time, a flexible adaptivity as well as a high reuse of technology, implementation concepts and existing software. Product

Data Management and Exchange

This project deals with the management and exchange of product data, covering the design stage as well as efficient and long-term storage of data during the whole product lifecycle. Though relational and object-oriented DBS already offer some basic support, most applications in this area have been developed using other solutions. Special emphasis has been put on the International Standard for the Exchange of Product Data (STEP), which defines the object-oriented data definition language EXPRESS as well as the navigational access interface SDAI (Standard Data Access Interface). Because of the heterogeneity and the distribution aspects especially component technology (e.g. CORBA, or web technology) has to be investigated for an effective usage.

Data Warehouse and Data Mining

Data warehousing and data mining is of vital importance to the integrated provision and analysis of data in enterprises. Research activities of the department AS in this field cover technology for data warehousing and data mining as well as va-rious application scenarios. On the technological level the focus lies on system architecture, middleware support, and the integration of operators into the database engine. In the application area we address the applicability of data mining in typical business environments and also investigate new fields of applications, which are not supported by data warehouses these days.

Workflow Management

During the last two years, research in the field of workflow management has become more and more important. Since 1987, our research group is involved in projects about the management of long-lived activities and their combination with traditional, transaction-oriented methods. In 1990, the concept of ConTracts was created. Since then, this concept has been systematically extended to a platform for efficient, fault tolerant workflow management systems.

Flow Control in Design Applications

In integrated computer supported design environments the designflow manager has to keep any cooperation and interaction of the design activities consistent. Those activities comprise all designing interactions and CAD tools. There are different layers of activity abstraction to be found, which build in a natural and system integrated way the typical structure of flow management in a tool oriented design environment. A typical design flow can be divided into interacting sub design flows, which can be well defined as flow protocols on the different activity layers. This project aims at developing corresponding design concepts to support flexible and layer specific control flow management, which compose an overall control flow management. In doing so, already existing concepts in the areas of transaction processing, workflow systems, and group work should be considered.

Geographic Information Systems and Spatially Aware Information Systems

With the growing interest in a computer supported presentation, administration and analysis of spatially referenced data the importance of geographic information systems (GIS) has increased significantly. The central component of GIS is a geographic or a spatial database system. These systems differ from the traditional data base management systems developed primarily for business and administration needs mainly by the fact that they offer special concepts and technologies especially for spatial data models and languages and efficient data structures for storage of and access to spatial data. In this project area we address questions concerning the system architecture of GIS, the design of geographical query languages, and especially the integration of geographic database systems based on object-relational technology. Spatially aware information systems can be seen as an evolvement of GIS, since it is an integration of GIS with location services that track the current positions of certain (moving or mobile) objects. With this, novel types application scenarios - that show a location awareness - can be supported.

Component Technology and Middleware

Modern information systems are characterized by a high degree of heterogeneity and distribution of software and hardware. This is especially true for most projects of the department "AS" (e.g. earth observation systems, geographical information systems, product data management systems, design control, etc). Moreover, these systems mostly consist of autonomous components (like e.g. database applications, TP monitors or user interaction). In order to cope with the complexity of such systems, it is necessary to model the entire system as a combination of separate components that interact via appropriate middleware. In this sense, the term middleware comprises file and database management systems, TP monitors, network services and e-mail systems, workflow systems as well as more complex frameworks like CORBA or DCOM. In this project area we will deal with the design and efficiency of such component-based systems. Particular emphasis will be put on efficient data access and data shipping techniques. The main goal is to design, implement and evaluate concepts for distributed (heterogeneous) data management supporting STEP-based applications, e.g. CAD tools or bill-of-material processing. Due to heterogeneity and distribution of components, modern concepts which support Intranet and Internet (like CORBA and Java) will be used and evaluated as well.

Federated Information Systems

Federated information systems are mainly built on middleware technology, and especially on database middleware like federated database systems and database gateways. From a technological point of view it has to be decided on how much integration of the component systems is needed versus how much component autonomy is required. First experiences show that for different application areas also different degrees of integration as well as different federation techniques are adequate. By means of the various federation projects in our department, we hope that we can detail our investigations on the appropriate federation techniques.