In the paper, we discuss the problem of approximate answers to queries in cooperative database systems (CDBS). CDBS give approximate answers when exact answers are empty or unavailable, and provide summary answers when answer sets are too large [6]. An approximate answer is an answer corresponding to a relaxed version of the query. The relaxation is obtained by means of replacement of equality relation by a partial ordering relation (in "child semantics") or by partial pre-ordering relation (in 'neighbor semantics"). The other type of relaxation discussed in the paper consists in introducing partial ordering into set of queries. Thus, instead of evaluating original query, a query subsuming it (more general) may be evaluated.
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