Efficiently and Effectively Answering Why-Not Questions based on Provenance Polynomials
Abstract
The problem of answering Why-Not questions consists in explaining why the result of a query
does not contain some expected data, i.e., missing answers. To solve this problem, we resort to identifying
where in the query, data relevant to the missing answer were lost. Existing algorithms producing such
query-based explanations rely on a query tree representation, potentially leading to different or partial
explanations. This significantly impairs on the effectiveness of computed explanations. Here we present an
effective, query-tree independent representation of query-based explanations, for a wide class of Why-Not
questions, based on provenance polynomials. We further describe an algorithm that efficiently computes the
complete set of these explanations. An experimental evaluation validates our statements
Origin | Files produced by the author(s) |
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