Pekka Kilpelainen. Tree Matching Problems with Applications to Structured Text Databases. PhD thesis, Dept. of Computer Science, University of Helsinki, 1992.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....and the query as labeled trees with a single node type. With this interpretation, the problem of answering a query can be mapped to the problem of embedding a query tree in a data tree. Our de nition of tree matching is inspired by the unordered path inclusion problem introduced by Kilpel ainen [Kil92] Unordered path inclusion is de ned as an injective function that preserves labels and parent child relationships, but not the order of the siblings. We think that ignoring the order of siblings is favorable or even necessary for querying XML data because the ordering of the elements or keywords ....

....the injectivity property of the embedding function then we would run into a complexity trap : The relaxation of the parent child relationship to an ancestor descendant relationship, which we will introduce in Section 4.2. 1, would lead to the unordered tree inclusion problem that is NP complete [Kil92] 6 4.2.1. Node Insertion: Moving to a more Speci c Context A node insertion creates a query that expects the matches of a query subtree in a more speci c context. We only allow the insertion of inner nodes, that is, every edge can be replaced by a node with an incoming and an outgoing edge. ....

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P. Kilpelainen. Tree Matching Problems with Applications to Structured Text Databases. PhD thesis, University of Helsinki, Finland, November 1992.

....answers. Since onedimensional formalisms are typically used to retrieve unrelated data items (such as articles, books, sections, letters, etc. of a particular type they are closely related to traditional information retrieval from a conceptual point of view. Multi dimensional formalisms such as [Kil92, DFF 98, CCD 99, AQM 97] by relating di erent parts of the data in each single answer, are closer to database formalisms. 2 Retrieval of structured information Di erent motivations exist for refering to distinct parts of the data in an answer. In many formalisms for semistructured ....

.... construct part of the query that lead to a satisfactory representation of the complete set of answers. This obligation is a major di erence to our approach, as we shall see below. Tree Matching One of the most natural multi dimensional query languages is Kilpel ainen s Tree Matching formalism [Kil92] In this approach, partial descriptions of trees are used 1 To answer questions of this type, databases with large collections of parsed sentences are currently under construction at several places, cf. IBR00, MSM93, OMM98] 4 as queries, and answers are formalized as homomorphic embeddings ....

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Pekka Kilpelainen. Tree Matching Problems with Applications to Structured Text Databases. PhD thesis, Dept. of Computer Science, University of Helsinki, 1992. 64

....compute all necessary term frequencies and inverse document frequencies at query time. In Section 8 we present rst experiences with the implementation of our approach. Finally, we review related work in Section 9, and give a conclusion in Section 10. 2 Tree Matching Kilpel ainen introduced in [Kil92] several variations of Tree Matching techniques as simple and intuitive means to answer queries over trees. We decided to use a slightly modi ed version [Meu00] of unordered tree inclusion as the most exible and powerful variant 1 . Figure 1 shows an unordered tree inclusion of a query tree in ....

P. Kilpelainen. Tree Matching Problems with Applications to Structured Text Databases. PhD thesis, University of Helsinki, Finland, November 1992.

....form of query answering which can be eciently computed. Note that for many novel applications such as e commerce such a cascade style query answering is needed [18] 8 Related Work Tree Databases: For tree queries and tree databases, a simpli ed form of CAA based on the Tree Matching formalism [20] has already been introduced in [25, 24] The present paper signi cantly extends over this early work. Query formalisms for semi structured data: Several query models for XML and semistructured data have been designed and or implemented and used [23, 3, 33, 15, 30, 31, 4, 10] cf. 4, 10] for ....

P. Kilpelainen. Tree Matching Problems with Applications to Structured Text Databases. PhD thesis, Dept. of Computer Science, University of Helsinki, 1992.

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Pekka Kilpelainen. Tree Matching Problems with Applications to Structured Text Databases. PhD thesis, Dept. of Computer Science, University of Helsinki, 1992.

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Pekka Kilpelainen. Tree Matching Problems with Applications to Structured Text Databases. PhD thesis, University of Helsinki, Department of Computer Science, November 1992.

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