"generic" dictionary rules A→B A∈V C , B∈V T "generic" phrase structure rules A→α A∈V X , α∈(V C ∪V X ) ＋ "specific" dictionary rules for request ID=i A→B A∈V C i , B∈V T "specific" phrase structure rules for request ID=i A→α A∈V X i , α∈ Fig.
compared to the Web or other open domain retrieval tasks, a manual/FAQ search is a very domain-specific task, where the terms used in documents and queries are limited, and this causes high overlapping among the terms of different queries.