Abstract. Advance Reservations are an important concept to support QoS and Workflow Scheduling in Grid environments. However, the impact of reservations from the Grid on the performance of local schedulers is not yet known. Using discrete event simulations we evaluate the impact of reservations on planning-based resource management of standard batch jobs. Our simulations are based on a real trace from the parallel workload archive. By introducing a new option for scheduling reservations in planning-based resource management, less reservation requests are rejected. Our results are important for increasing the acceptability of the Grid technology. We show, that a limited number of additional resource reservations from the Grid have only a limited impact on the performance of the traditionally submitted batch jobs.
In large-scale distributed systems, information is typically generated decentralized. However, for many applications it is desirable to have a unified view on this knowledge, allowing to query it without regarding the heterogeneity of the underlying systems. In this context, two main requirements have to be fulfilled. On the one hand, we need a flexible knowledge representation, and on the other hand the underlying infrastructure and query evaluation algorithm has to be highly scalable.The combination of p2p networks as basic infrastructure with RDF as a knowledge representation is a promising approach to this problem. Within this paper, we focus on the evaluation of RDF queries with respect to RDF data stored in a DHT-based p2p network. We propose a query algorithm and research different optimizations based on a look-ahead technique and Bloom filters which aim at maximizing the throughput and scalability of the entire system.
In this paper we present a concept and prototypical implementation of a software system (aSQLg) to automatically assess SQL statements. The software can be used in any introductory database class that teaches students the use of SQL. On one hand it increases the efficiency of grading students submissions of SQL statements for a given problem statement by automatically determining a score for the statement based on different aspects. On the other hand it may also be used to improve student learning of SQL statements by enabling them to continuously (re-)submit their solutions and determine improvements in quality by comparing the automatically determined scores. In order to keep the administrative overhead for using it minimal we have implemented the software in a way that it may be plugged into any course/learning management system with minimal overhead. We have used it in conjunction with WebCAT as well as our own proprietary course management system. Student feedback collected after its first usage in a database class shows promising results for future usage of the system.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.