12.3 Natural laNguage INterfaCe to uNstruCtured data 331
In order to tolerate lexical variations in the input questions, the prepro-
cessor builds a semantic knowledge base composed of interpretation rules
and semantic sets for all possible relationship and attribute names in the da-
tabase. This helps to build the same semantic representation, and hence, the
same SQL query for various questions.
In the preceding NLI2DB example, we saw that the link parser, which
collects information at a syntactic level, also can be used at a semantic level.
The focus of NLI2DBs today has shifted to handle problems at a higher level
of linguistic analysis. Therefore, the development of NLI2DB systems that
handle language-related phenomena is an active area ...