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Synchronous context-free grammar
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<h2 id="formalism">Formalism</h2> <p>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<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> gives the Chinese/English example: </p> <i>X</i> → (yu <i>X</i>1 you <i>X</i>2, have <i>X</i>2 with <i>X</i>1) <p>This rule indicates that an X phrase can be formed in Chinese with the structure "yu <i>X</i>1 you <i>X</i>2", where <i>X</i>1 and <i>X</i>2 are variables standing in for subphrases; and that the corresponding structure in English is "have <i>X</i>2 with <i>X</i>1" where <i>X</i>1 and <i>X</i>2 are independently translated to English. </p> <h2 id="software">Software</h2> <ul><li><a href="http://cdec-decoder.org">cdec</a>, MT decoding package that supports SynCFGs</li> <li><a href="http://joshua-decoder.org">Joshua</a>, a machine translation decoding system written in Java</li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Chiang, David (2007). "Hierarchical phrase-based translation". Computational Linguistics. 33 (2): 201–228. doi:10.1162/coli.2007.33.2.201. S2CID 3505719. <a href="https://doi.org/10.1162%2Fcoli.2007.33.2.201" target="_blank">https://doi.org/10.1162%2Fcoli.2007.33.2.201</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Venugopal, Ashish; Zollmann, Andreas; Vogel, Stephan (2007). "An efficient two-pass approach to Synchronous-CFG driven statistical MT". Proc. NAACL HLT. pp. 500–507. <a href="https://www.aclweb.org/anthology/N07-1063" target="_blank">https://www.aclweb.org/anthology/N07-1063</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Chiang, David (2007). "Hierarchical phrase-based translation". Computational Linguistics. 33 (2): 201–228. doi:10.1162/coli.2007.33.2.201. S2CID 3505719. <a href="https://doi.org/10.1162%2Fcoli.2007.33.2.201" target="_blank">https://doi.org/10.1162%2Fcoli.2007.33.2.201</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> </ol>