Entailment pair extension apparatus, computer program therefor and question-answering system

An entailment pair extension apparatus for extending entailment pairs by generating n-term entailment pairs from m-term entailment pairs, said entailment pair extension apparatus comprising:

• generation rule storage means comprising a non-transitory computer readable medium for storing generation rules for generating said n-term entailment pairs from said m-term entailment pairs, wherein:
• m and n are integer not smaller than 0 and satisfying m <n;
• each of said m-term entailment pairs include a first language pattern and a second language pattern;
• the first language pattern and the second language pattern each comprise a combination of a verb phrase and m terms;
• the second language pattern has a semantic relation with the first language pattern such that the verb of the first language pattern entails the verb of the second language pattern;
• said generation rules each define:
• a condition to be satisfied by an m-term entailment pair before said generation rule is applied to the m-term entailment pair, and
• a language pattern modification rule specifying:
• for each of the language patterns constituting said m-term entailment pair, addition of n minus m variables to the language pattern by adding one or more variables at one or more locations in the language pattern if said condition is satisfied;
• a processor configured to generate an n-term entailment pair from each m-term entailment pair of the m-term entailment pairs by:
• receiving said m-term entailment pair;
• for each of the generation rules stored in said generation rule storage means, determining whether or not the m-term entailment pair satisfies the condition of the generation rule;
• and
• when said modification rule of the generation rule is determined to be satisfied, applying said modification rule to each language pattern constituting said m-term entailment pair to generate, the n-term entailment pair;
• and
• storing the n-term entailment pair generated by applying said modification rule.