How Hard is it to Decide if a Fact is Relevant to a Query?
We consider the following fundamental problem: given a database D, Boolean conjunctive query (CQ) q, and fact f in D, decide whether f is relevant to q wrt. D, i.e., does f belong to a minimal subset S of D such that S |= q. Despite being of central importance to query answer explanation, the combined complexity of deciding query relevance has not been studied in detail, leaving open what makes this problem hard, and which restrictions can yield lower complexity. Relevance has already been shown to be harder than query evaluation: namely, $Σ^p_2$-complete for CQs, even over a binary signature. We further observe that NP-hardness applies already to (acyclic) chain CQs. Our work identifies ...
| Authors | Meghyn Bienvenu, Diego Figueira, Pierre Lafourcade |
|---|---|
| Primary category | cs.DB |
| Published | 24 April 2026 |
| Last updated at source | 24 April 2026 |
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