Partial Evaluations in a Set-Theoretic Query Language for the WWW

摘要

We present an approach to handle unavailable data sources during query execution over WWW which is based on partial evaluations. Syntax of the set-theoretic query language triangle open and some examples of queries are given. We define an ordinary and a lazy semantics for this language, Moreover, are introduce a universe of non-well-founded hereditarily finite protosets and an approximation relation on this universe in order to compare the partial answers to a query. A theorem about properties of the above semantics, in particular about correctness of lazy semantics is formulated.