Yehoshua Sagiv

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)
TSIMMIS—The Stanford-IBM Manager of Multiple InformationSources—is a system for integrating information. It offers a datamodel and a common query language that are designed to support thecombining of information from many different sources. It also offerstools for generating automatically the components that are needed tobuild systems for integrating(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 bottomUP (= forward chaining) in a way that cuts down on the irrelevant facts that are generated. The advantage of(More)
Queries in relational databases can be formulated in terms of relational expressions using the relational operations select, project, join, union, and difference The equivalence problem for these queries is studied with query optimization m mind It ts shown that testmg eqmvalence of relational expressions with the operators select, project, join, and union(More)
1 Introduction Recent yeara saw several proposals for languages for querying object-oriented databases [2, 3, 4, 5, 13, 6]. None of them, however , captures (or even attempts to deal with) all the aspects of the object-oriented model. In this paper, we present a new query language, henceforth referred to as XSQL, that incorporates fea tures not found in(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)
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)
In keyword search over data graphs, an answer is a nonredundant subtree that includes the given keywords. An algorithm for enumerating answers is presented within an architecture that has two main components: an <i>engine</i> that generates a set of candidate answers and a <i>ranker</i> that evaluates their score. To be effective, the engine must have three(More)