In this paper, the benefits of parallel computing using a workstation cluster are explored for satellite orbit prediction. Data and function decomposition techniques are used. Speedup and throughput are the performance metric studied. The software employed for parallelization was the Parallel Virtual Machine (PVM) developed by the Oak Ridge National Laboratory. PVM enables a network of heterogeneous workstations to appear as a parallel multicomputer to the user programs. A speedup of almost 6 was achieved when using 8 SUN workstations.
The key driving force behind general-purpose enterprise directory services is for providing a central repository for commonly and widely used information such as users, groups, network service access information and profiles, security information, etc. Acceptance of the Lightweight Directory Access Protocol (LDAP) as an access protocol has facilitated widespread integration of these directory services into the network infrastructure and applications.Both directory and relational databases are data repositories sharing the characteristic that they have mechanisms for dealing with schema and structure of information and are suitable for systematically organized data. This tutorial describes characteristics of directories such as schema information, query language and support, storage mechanisms required, typical requirements imposed by applications, etc. We then explain the differences between a directory and relational database, and show how the two are required to co-exist in a typical enterprise.An essential characteristic assumed for information stored in directories is that it is relatively static and that the queries are mostly read only. We describe typical directory applications to validate this assumption and project the requirements imposed on them as these applications evolve. We then describe areas of overlap between traditional databases and directories, describe some database and directory integration solutions adopted in the market, and identify areas in which directory deployment can benefit from the experience gathered by the database community. Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without lee provided that copies are not made or distributed for profit or commercial advant -age and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. ACM SIGMOD 2000 5/00 Dallas, TX, USA
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