Recursive queries and context-free graph grammars
نویسندگان
چکیده
منابع مشابه
Recursive Queries and Context-free Graph Grammars
The semantics of a recursive query in the context of a relational database can be formalized in terms ofa context-free graph grammar associated with it. This grammargenerates oriented, labeled hypergraphs. The labels of the hypercdges of these hypergraphs, called the computation graphs of the query, are the names of the relations forming the database under consideration. Some
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Graph grammars have been studied by several authors. The motivations of these works have arisen from completely different areas of computer science, such as picture processing (Pfaltz and Rosenfeld, 1969; Montanari, 1970; Rosenfeld and Milgram, 1972; Pavlidis, 1972; Abe et al., 1973; Furtado and Mylopoulos, 1975; Fu and Brayer, 1975) or formal semantics of programming languages (Pratt, 1971). I...
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Context-free grammars are fundamental for the description of linguistic syntax. However, most artificial grammar learning experiments have explored learning of simpler finite-state grammars, while studies exploring context-free grammars have not assessed awareness and implicitness. This paper explores the implicit learning of context-free grammars employing features of hierarchical organization...
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We consider the problem of parsing non-recursive context-free grammars, i.e., context-free grammars that generate finite languages. In natural language processing, this problem arises in several areas of application, including natural language generation, speech recognition and machine translation. We present two tabular algorithms for parsing of non-recursive context-free grammars, and show th...
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Probabilistic context-free grammars (PCFGs) provide a simple way to represent a particular class of distributions over sentences in a context-free language. Efficient parsing algorithms for answering particular queries about a PCFG (i.e., calculating the probability of a given sentence, or finding the most likely parse) have been developed, and applied to a variety of patternrecognition problem...
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ژورنال
عنوان ژورنال: Theoretical Computer Science
سال: 1991
ISSN: 0304-3975
DOI: 10.1016/0304-3975(51)90009-6