| 摘要: |
| 给出了上下文无关文法(context-free grammar,简称CFG)产生式集的一种划分方法,可将产 生式分为两类.使用一类产生式进行推导时,推导过程将无限进行下去;使用另一类进行推导 时,推导过程将迅速结束.证明了CFG句子生成过程一定是先使用一类产生式使生成的句型不 断变长、变复杂,再使用另一类产生式使句型变成句子.据此，提出了一种可控制的通用句子 生成方法.其生成一条句子的时间和空间复杂度是O(r+n),其中n是生成句子的长度或深度 限制 |
| 关键词: 上下文无关文法,产生式集合,产生式集合划分, 句子生成,句子生成策略. |
| DOI： |
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| 基金项目:本文研究得到国家自然科学基金(No.69873042)和国家“九五”重点科技攻关项目基 金(No.96-729-06-02)资助. |
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| Generating Sentences of CFL Based on Partition of CFG Production Set |
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WANG Hong-hao,DONG Yun-mei
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| Abstract: |
| In this paper, a method is presented to partition productions of CFG (context-f ree grammar). It divides production set into two parts. The derivation with prod uctions in one part will never terminate, while it must terminate rapidly with p roductions in the other part. It is proved that the procedure of generating sent ences of CFL (context-free language) is using productions in one part to make t he sentential form longer and more complex first, and then using productions in the other part to terminate the procedure. A general controllable method is atta ined for generating sentences of CFL with restricted length or depth. The time a nd space complexity for generating one sentence is O(r+n), where n is th e restricted length or depth of sentences and r is the number of productions in given CFG. The generating strategies for different conditions are also discu ssed. |
| Key words: CFG (context-free grammar), production set, production set partition, sentence generation, sentence generating strategy. |
