Query evaluation based on domain-specific ontologies

We describe here a query evaluation principle that is based on compound or hierarchical aggregation, where an aggregate may be an argument to another aggregate. A query is assumed to consist of or be decomposed into a set of query attributes that are divided into groups. During query evaluation, groups are treated for individual aggregation and group aggregates are in turn aggregated, leading to a query aggregate. The evaluation principle is considered in the context of an approach to ontology-based querying, where domain knowledge in the form of a dictionary and an ontology is utilized in the computation of groups of attributes and aggregation parameters. While the user may pose a query in a simple form as a list of words or in natural language, queries are evaluated as compound expressions. The groupings and operators applied are the results of a knowledge-based manipulation of the initial query.