An approach to knowledge-based query evaluation

We describe here a query evaluation principle based on hierarchical aggregation. Queries are assumed to be free form expressions of lists of words unconnected or forming fragments of natural language (NL). A query is transformed into a nested structure of subsets of attributes. During query evaluation, each subset is treated for individual aggregation and aggregates are thus in turn aggregated, leading to an aggregate for measuring the full query against an object from the database. The key idea with the described principle is to obtain a knowledge-based query evaluation. This is obtained by initiating the query evaluation process through manipulation based on knowledge in a domain-specific knowledge base. An experimental prototype system implementing this line of query evaluation is described. (C) 2003 Elsevier B.V. All rights reserved.