Alberto O. Mendelzon

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The World Wide Web is a large, heterogeneous, distributed collection of documents connected by hypertext links. The most common technology currently used for searching the Web depends on sending information retrieval requests to "index servers" that index as many documents as they can find by navigating the network. One problem with this is that users must(More)
url: y’!!!!.Url ] as “pubsDb: insert” from X in browse(“http://a.b.c/papers.html”)’, y in X!’ where X.Tag = “H2” Variable X is successively instantiated to each tail whose first descendant is a group name and whose second descendant represents the list of papers for the group; y is then instantiated to each paper. Note that there is no SCAN(More)
Current day database applications, with large numbers of users, require fine-grained access control mechanisms, at the level of individual tuples, not just entire relations/views, to control which parts of the data can be accessed by each user. Fine-grained access control is often enforced in the application code, which has numerous drawbacks; these can be(More)
The popularity of the World-Wide Web (WWW) has made it a prime vehicle for disseminating information. The relevance of database concepts to the problems of managing and querying this information has led to a significant body of recent research addressing these problems. Even though the underlying challenge is the one that has been traditionally addressed by(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)