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Synchronous context-free grammars (SynCFG or SCFG; not to be confused with stochastic CFGs) constitute a formal model of natural language syntax, developed in the area of statistical machine translation (MT). The theory of SynCFGs borrows from syntax-directed transduction and syntax-based machine translation, modeling the reordering of clauses that occurs when translating a sentence by correspondences between phrase-structure rules in the source and target languages. Performance of SCFG-based MT systems has been found comparable with, or even better than, state-of-the-art phrase-based machine translation systems. Several algorithms exist to perform translation using SynCFGs. ==Formalism== Rules in a SynCFG are superficially similar to CFG rules, except that they specify the structure of two phrases at the same time; one in the source language (the language being translated) and one in the target language. Numeric indices indicate correspondences between non-terminals in both constituent trees. Chiang〔 gives the Chinese/English example: : (yu you , have with ) 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Synchronous context-free grammar」の詳細全文を読む スポンサード リンク
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