Study of Cover Ratio of Syntactic Sentence Patterns for Japanese Complex Sentences

Pattern based MT has drawn attention for long time since it yields good translationsfor matched sentences. But it has been difficult problem how to build the patternpair dictionaries which have a huge number of semantically independent patterns toobtain a high cover ratio.This paper experimentally evaluated the cover ratio ofthe pattern pair dictionary which has recently been developed for Japanese Complexand Compound sentences and studied possibility of pattern based MT method. This dictionary contains syntactic sentence patterns of Word Level (121, 000 patterns), Phrase Level (88, 000 patterns) and Clause Level (11, 000 patterns) which are generatedfrom 150, 000 example sentence pairs for Japanese to English.Evaluation wasconducted by using 4 parameters such as “Sentence Recall Ratio, ” “Sentence Coincide Ratio, ” “Semantic Precision Ratio, ” and “Matched Pattern Precision Ratio.” The results are as follows. “Sentence Recall Ratios” are 70%, 89% and 78% foreach of Word level, Phrase Level and Clause Level sentence patterns, and “Matched Pattern Precision Ratio” of Word Level sentence patterns is 21%. Though “Matched Pattern Precision Ratio” was low, it was carified that there are many ways left toincrease the matched patterns.