Learn More
XSEarch, a semantic search engine for XML, is presented. XSEarch has a simple query language , suitable for a naive user. It returns semantically related document fragments that satisfy the user's query. Query answers are ranked using extended information-retrieval techniques and are generated in an order similar to the ranking. Advanced indexing techniques(More)
We consider the problem of computing answers to queries by using materialized views. Aside from its potential in optimizing query evaluation, the problem also arises in applications such as Global Information Systems, Mobile Computing and maintaining physical data independence. We consider the problem of nding a rewriting of a query that uses the(More)
Several methods for implementing database queries expressed as logical rules are given and they are compared for efficiency. One method, called " magic sets, " is a general algorithm for rewriting logical rules so that they may be implemented bottom-UP (= forward chaining) in a way that cuts down on the irrelevant facts that are generated. The advantage of(More)
Query evaluation over probabilistic XML is explored. The queries are twig patterns with projection, and the data is represented in terms of three models of probabilistic XML (that extend existing ones in the literature). The first model makes an assumption of independence among the probabilistic junctions, whereas the second model can encode probabilistic(More)
Constraints are a valuable tool for managing information across multiple databases, as well as for general purposes of assuring data integrity. However, efficient implementation of constraint checking is difficult. In this paper we explore techniques for assuring constraint satisfaction without performing a complete evaluation of the constraints. We(More)
When integrating heterogeneous information resources , it is often the case that the source is rather limited in the kinds of queries it can answer. If a query is asked of the entire system, we h a ve a new kind of optimization problem, in which w e m ust try to express the given query in terms of the limited query templates that this source can answer. For(More)
Various approaches for keyword proximity search have been implemented in relational databases, XML and the Web. Yet, in all of them, an answer is a <i>Q</i>-fragment, namely, a subtree <i>T</i> of the given data graph <i>G</i>, such that <i>T</i> contains all the keywords of the query <i>Q</i> and has no proper subtree with this property. The rank of an(More)
Presented is a computation method&#8212;the <italic>chase</italic>&#8212;for testing implication of data dependencies by a set of data dependencies. The chase operates on tableaux similar to those of Aho, Sagiv, and Ullman. The chase includes previous tableau computation methods as special cases. By interpreting tableaux alternately as mappings or as(More)