Patent Document ID: 8862468
Application ID: 13334580

Base Claim:
1. A method of refining a context-free grammar, the method comprising: generating backoff grammar rules from rules of an initial context-free grammar, each backoff grammar rule being generated based on at least one keyword identified from the initial context-free grammar; and recursively modifying the initial context-free grammar using a computer processing unit, wherein recursively modifying comprises: obtaining a relined context-free grammar by modifying the initial context-free grammar,during a first iteration, based at least in part on recognition of utterances using the backoff grammar rules; determining a recognition efficiency of the refined context-free grammar and the hackoff grammar rules to the utterances; and during each of at least one additional iteration, further modifying the refined context-free grammar based at least in part on recognition of utterances using the refined context free grammar and backoff grammar rules until the refined context-free grammar and the backoff grammar rules meet a threshold level of recognition efficiency.

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Claim 2:
2. The method of claim 1 , wherein modifying the initial context-free grammar comprises selecting, based at least in part on a statistic derived from application of the backoff grammar rules, a sub-set of a collection of utterances for transcription, the sub-set being fewer than all of the utterances in the collection.