7. The method of claim 1 , wherein determining the normalized relevance scores for the input query text corresponding to the multiple domains comprises, for a domain of the multiple domains: sequencing the input query text into at least one sequence of substrings; tokenizing the at least one sequence of substrings into a set of token sequences comprising at least one token sequence with respect to the domain based on the ontology of the query model for the domain; obtaining a set of normalized relevance measures with respect to the domain, each normalized relevance measures corresponding to one token sequence of the set of token sequences of the domain based on trigrams appearing in the one token sequence and the trigram corpus of the domain; and determining, as one of the normalized relevance scores for the input query text corresponding to the multiple domains, a normalized relevance score with respect to the domain for the input query text based on the set of normalized relevance measures with respect to the domain.
7. The method of claim 1 , wherein determining the normalized relevance scores for the input query text corresponding to the multiple domains comprises, for a domain of the multiple domains: sequencing the input query text into at least one sequence of substrings; tokenizing the at least one sequence of substrings into a set of token sequences comprising at least one token sequence with respect to the domain based on the ontology of the query model for the domain; obtaining a set of normalized relevance measures with respect to the domain, each normalized relevance measures corresponding to one token sequence of the set of token sequences of the domain based on trigrams appearing in the one token sequence and the trigram corpus of the domain; and determining, as one of the normalized relevance scores for the input query text corresponding to the multiple domains, a normalized relevance score with respect to the domain for the input query text based on the set of normalized relevance measures with respect to the domain. 13. The method of claim 7 , wherein determining the normalized relevance measure with respect to the domain for the input query text comprises determining as the normalized relevance measure for the input query text a maximum relevance measure among the set of normalized relevance measures with respect to the domain each corresponding to one token sequence of the set of token sequences.