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A simple parse tree. A parse tree is made up of nodes and branches. [4] In the picture the parse tree is the entire structure, starting from S and ending in each of the leaf nodes (John, ball, the, hit). In a parse tree, each node is either a root node, a branch node, or a leaf node. In the above example, S is a root node, NP and VP are branch ...
Generalized phrase structure grammar (GPSG) is a framework for describing the syntax and semantics of natural languages. It is a type of constraint-based phrase structure grammar . Constraint based grammars are based around defining certain syntactic processes as ungrammatical for a given language and assuming everything not thus dismissed is ...
Tree-adjoining grammars are somewhat similar to context-free grammars, but the elementary unit of rewriting is the tree rather than the symbol. Whereas context-free grammars have rules for rewriting symbols as strings of other symbols, tree-adjoining grammars have rules for rewriting the nodes of trees as other trees (see tree (graph theory ...
Dependency, in contrast, is a one-to-one relation; every word in the sentence corresponds to exactly one node in the tree diagram. Both parse trees employ the convention where the category acronyms (e.g. N, NP, V, VP) are used as the labels on the nodes in the tree.
Treebanks are necessarily constructed according to a particular grammar. The same grammar may be implemented by different file formats. For example, the syntactic analysis for John loves Mary , shown in the figure on the right/above, may be represented by simple labelled brackets in a text file, like this (following the Penn Treebank notation):
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In computer science, an ambiguous grammar is a context-free grammar for which there exists a string that can have more than one leftmost derivation or parse tree. [ 1 ] [ 2 ] Every non-empty context-free language admits an ambiguous grammar by introducing e.g. a duplicate rule.
The term phrase structure grammar was originally introduced by Noam Chomsky as the term for grammar studied previously by Emil Post and Axel Thue (Post canonical systems). Some authors, however, reserve the term for more restricted grammars in the Chomsky hierarchy : context-sensitive grammars or context-free grammars .