, but observe that any sequential top-k query processing strategy is bound to require unnecessarily long query processing times, since web accesses exhibit high and variable latency. Fortunately, web sources can be probed in parallel, and each source can typically process concurrent requests, although sources

and optimization of XML query processors are the upcoming issues. Following a long tradition in database research, we provide a framework to assess the abilities of an XML database to cope with a broad range of different query types typically encountered in real-world scenarios.

Query expansion methods have been studied for a long time - with debatable success in many instances. In this paper we present a probabilistic query expansion model based on a similarity thesaurus which was constructed automatically. A similarity thesaurus reflects domain knowledge about

Query expansion has long been suggested as an effective way to resolve the short query and word mismatching problems. A number of query expansion methods have been proposed in traditional information retrieval. However, these previous methods do not take into account the specific characteristics

, a user subscription may consist of an interest in an airplane of a certain type, not to exceed a certain price. A published event may consist of an offer of an airplane with certain properties including price. A subscription closely resembles a trigger in that it is a long-lived conditional query

ABSTRACT Due to the enormous increase in the stored digital contents, search and retrieval functionalities are necessary in multimedia systems. Though processor speed for standard PCs (Personal Computers) is experiencing an almost exponential growth, the memory subsystem handicapped by lower frequencies and a physical I/O (Input/Output) limitation reflects the bottleneck of common computer architectures. As a result, many applications such as database management systems, remain so dependent on memory throughput that increases in CPU (Central Processing Unit) speeds are no longer helpful. Because average bandwidth is crucial for system performance, our research has focused especially on techniques for efficient storage and retrieval of multimedia data. This paper presents the realization of a hardware database search engine based on an associative access method for textual information retrieval. It reveals the internal architecture of the system and compares the results of our hardware prototype with the software solution.

's performance. At the same time, querying remote sources may be very expensive because of high connection overhead, long computation time, financial charges, and temporary unavailability. We propose a costbased optimization technique that caches statistics of actual calls to the sources and consequently

Long queries form a difficult, but increasingly important segment for web search engines. Query reduction, a technique for dropping unnecessary query terms from long queries, improves performance of ad-hoc retrieval on TREC collections. Also, it has great potential for improving long web queries

results showing the importance of corpus-dependent baseline summarization standards, compression ratios and carefully crafted long queries.

has long supported subquery predicates, which may be arbitrarily time-consuming to check. Thus restrictions should not be considered zero-time operations, and the model of query optimization must be enhanced. In this paper we develop a theory for moving expensive predicates in a query plan so