Abstract: A multi-clip query requests multiple video clips. We address the multi-clip query optimization problem. We propose a new heuristic called restricted search interval that maximizes clip sharing between queries and consequently reduces the workload of the video server. The experimental results show that the suggested heuristics reduce the server workload by about 68.7% in comparison to a classical heuristic approach.

Abstract: This paper presents the parallel video server SESAME-KB, by the means of its architectural design, striping, scheduling, caching and admission policy. Furthermore we compare our prototype to approaches which influenced our realization. Keywords: Parallel Video Server, Parallel Systems and Communication.

Abstract: This paper compares different selected and representative parallel video servers, including our server SESAME-KB, by the means of their architectural design, striping, scheduling, caching and admission policy. It is shown that these parallel video servers can support a high number of concurrent accesses, but will also reveal missing components, as bottlenecks. Finally we point to further developments

Abstract: The Multimedia Storage and Retrieval System described in this paper is aimed at storing and retrieving medical multimedia data such as images and videos. There are three significant problems that automatically need to be addressed: providing enough capacity to fit Terabytes of MPEG files, efficient extraction of video fragments from MPEG files and quality of service issues. We are working on two different approaches to build MMSRS. The first one, described in this article, utilizes commercial HSM software for managing the tertiary storage hardware. The second approach that we have started to investigate is an attempt to build a specialised storage management system from scratch.

Abstract: This paper focuses on parallel query optimization. We consider the operator problem and introduce a new class of execution strategies called Linear-oriented Bushy Trees (LBT). Compared to the related approach of the General Bushy Trees (GBT) a significant complexity reduction of the operator ordering problem can be derived theoretically and demonstrated experimentally (e.g. compared with GBTs, LBTs authorize optimization time improvement that can reach up to 49%) without losing quality. Finally we demonstrate that existing commercial parallel query optimizers need little extension mod ifications in order to handle LBTs.

Abstract: Es läuft eine spannende Diskussion darüber, wie früh man Kinder an den Computer heranführen sollte. Jenseits solcher Intellektuellen-Diskussionen machen manche Firmen schon seit Jahren enorme Geschäfte mit Software und Hardware für Kinder im Kindergartenalter. Auch der erste Computer für Babys hat schon seinen Siegeszug auf dem amerikanischen Markt angetreten. Mit den Geschäftemachern zu diskutieren, ist wahrscheinlich nicht viel klüger als gegen Windmühlen zu kämpfen. Diese Firmen könnten ihre Geschäfte nicht machen, wenn es nicht viele Eltern, Großeltern, Pädagogen und Psychologen gäbe, die den Computer kleinen Kindern mit guter Absicht in die Hand geben. Die folgende Diskussion spricht die wohlwollenden Erwachsenen an, die sich für Kinder verantwortlich fühlen und sich nicht entscheiden können, wann und wie Kinder mit dem Phänomen Computer konfrontiert werden sollten.

Abstract: Object-Oriented Technology.

Abstract: The Workflow Management System AltaVista Works has been extended to be able to process workflows in a distributed, partly even parallel manner. Build-time data are replicated over all participating workflow servers. The distribution of workflow execution is based on migration. Instead of the usual static re-partitioning, a highly dynamic management of distribution is applied.

Abstract: This paper describes the PARMED project initiative The aim of PARMED is to provide medical stu with a large virtual database of image and video data distributed over several medical centers Clients can access the PARMED system by an active client software which provides graphical interfaces to query the virtual database Incoming video streams and image data is postprocessed by the active client software to allow analysis of this data for diagnostics or virtual teaching Quality of service and security aspects are crucial for such kind of distributed system and will be addressed with priority

Abstract: Diverging demands on computer networks, such as high bandwidth, guaranteed quality of service and low latency lead to growing heterogeneity. IEEE1394-1995 is a standardized low-cost highperformance serial-bus-system with both isochronous and asynchronous operation. It might be an interesting candidate for all-round local and system area networks, providing a good compromise in fulfilling the above demands for low costs. Beside providing some technical background we show the possibilities and advantages of building parallel clusters on top of IEEE1394-1995. The main advantage is that minimal speed-up can be guaranteed, as shown on the basis of the parallel implementation of discrete Fourier transformation.

Abstract: An approach is introduced for semi-automatic parallelization of object-oriented simulations. The basic idea is to prepare parallelization at the earliest possible stage in the life-cycle of the creation of new simulations (i.e. at modeling), thus minimizing causality conflicts at run-time. The object-oriented model of a simulation is enriched by hints, describing the estimated load and communication costs between major classes and objects. This helps to grasp the inherent parallelism of the model. Based on this additional information, a partitioning with minimal communication between partitions can be generated automatically. Remaining dependency-conflicts must be resolved at run-time. The GoSim [A. Stopper, GoSim, ein Ansatz zur Beschleunigung diskreter, objektorientierter, verteilter Simulationen, Ph.D. Thesis, Institute of Informatics, University Klagenfurt, 1997] simulation system is presented, which implements the described proposal and provides semi-automatic parallelization of large-scale and/or high-performance simulations. It provides a description language, a partitioning tool, a program-skeleton generator and a simulation engine. Some measurements prove the usability of the approach.

Abstract: A method for evaluating several aspects of the performance of object oriented middleware is introduced. Latency, data transfer, parameter marshalling and scalability are considered. A portable benchmark toolkit has been developed to implement the method. A number of actual middleware products have been measured, such as C++ and Java based CORBA implementations, DCOM and Java/RMI. The measurements are evaluated and related to each other.

Abstract: This book constitutes the joint refereed post-proceedings of 20 workshops, one panel session, and one poster session held during the 13th European Conference on Object-Oriented Programming, ECOOP'99, in Lisbon, Portugal in June 1999. The volume presents overviews of the 20 workshops as well as more than 200 individual short presentations by the contributing authors in a coherent and systematic way. The wealth of up-to-date information provided spans the whole spectrum of object technology, from theoretical and foundational issues to applications in various domains.

Abstract: Aliasing in Object-Oriented Systems.

Abstract: This short paper presents a system offering parallel persistent and polymorphic sets of objects, on the level of an existing general purpose object-oriented programming language, like Modula-3 and JAVA. The user of such a system gets distribution and persistence in the same natural way, as users of traditional systems get volatile arrays of numbers of objects. In addition, advantages are taken from sophisticated optimization techniques.

Abstract: Even the more or less "canonical'', lower-level architecture of information systems needs to be revisited from time to time. Notions like persistence and transactions belong traditionally to the area of database management systems. There are, however, many applications, such as CAD, VLSI design or simulation, which need persistence and could take advantage of transactions, but require especially fast implementations not provided by DBMS. In this paper we are describing a low-level transaction concept used to implement our parallel main memory object store (PPOST), to provide main memory access times combined with the safety and convenience of transactions.

Abstract: The choice of the first-course programming language for a university-level computer science curriculum has pedagogical ramifications in terms of comprehensibility and mastery of fundamental concepts. This paper compares the merits of Java and Modula-3 as a first-course language.

Abstract: Choosing the "First Computer Language" is still a crucial issue. While the debate is quite often conducted on the language level, the arguments for making the choice are rather of much deeper methodological, didactical, and non-technical nature. Here, we describe the decision process that lead us to choose Modula-3 as the first language to be taught to informatics students at the Universität Klagenfurt and report on the experience gained.