Yaacov Y. Weiss

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When a query is evaluated under bag semantics, each answer is returned as many times as it has derivations. Bag semantics has long been recognized as important, especially when aggregation functions will be applied to query results. This paper is the first to focus on bag semantics for XPath queries. In particular, the problem of bag-equivalence of a large(More)
Formulating an XPath query over an XML document is a difficult chore for a non-expert user. This paper introduces a novel approach to ease the querying process. Instead of specifying a query, the user simply marks <i>positive examples</i> &#967;<sup>+</sup> of nodes that fit her information need. She may also mark <i>negative examples</i>(More)
This paper investigates the problem of learning tree patterns that return nodes with a given set of labels, from example graphs provided by the user. Example graphs are annotated by the user as being either positive or negative. The goal is then to determine whether there exists a tree pattern returning tuples of nodes with the given labels in each of the(More)
This article investigates the problem of learning tree patterns that return nodes with a given set of labels, from example graphs provided by the user. Example graphs are annotated by the user as being either <i>positive</i> or <i>negative</i>. The goal is then to determine whether there exists a tree pattern returning tuples of nodes with the given labels(More)
This paper investigates the problem of reverse engineering, i.e., learning, select-project-join (SPJ) queries from a user-provided example set, containing positive and negative tuples. The goal is then to determine whether there exists a query returning all the positive tuples, but none of the negative tuples, and furthermore, to find such a query, if it(More)
When a query is evaluated under bag semantics, each answer is returned as many times as it has derivations. Bag semantics has long been recognized as important, especially when aggregation functions will be applied to query results. This article is the first to focus on bag semantics for tree pattern queries. In particular, the problem of bag equivalence of(More)
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