Flexible Querying of Semi-Structured Data: a Fuzzy Set-Based Approach
Résumé
This article provides a general discussion about how flexible querying can be applied to semi-structured data~SSD!. We adapt flexible querying ideas, already used for classically structureddatabases, to XQuery-like querying of SSD for managing users’ priority and preferences, butalso for tackling with the variability of SSD underlying structures. Indeed flexible queryingseems to be still more useful for SSD than for classical databases, because of the potentialstructural heterogeneity of the former. Fuzzy sets are useful for expressing flexible require-ments on attribute values and for estimating the degree of similarity of tags, or attribute labels,with elements present in the request. Priorities are introduced in the request for specifying therelative importance of elementary requirements in terms of their semantic contents, but alsopreferences about the location of information in the structure. The evaluation of the queriesuses a qualitative scale with a finite number of levels, and retrieved pieces of SSD are rank-ordered using a lexicographic vector procedure. Illustrative examples are provided.