Tractable Conjunctive Queries over Static and Dynamic Relations

TL;DR

This paper characterizes classes of conjunctive queries over static and dynamic relations that allow for constant-time updates and enumeration, considering the interaction between static and dynamic data.

Contribution

It introduces a syntactic characterization of tractable conjunctive queries over static and dynamic relations, accounting for their interaction and providing complexity bounds.

Findings

Identifies three classes of tractable queries with constant update and enumeration delay.

Provides complexity bounds for preprocessing based on query class.

Shows that interaction between static and dynamic relations affects tractability.

Abstract

We investigate the evaluation of conjunctive queries over static and dynamic relations. While static relations are given as input and do not change, dynamic relations are subject to inserts and deletes. We characterise syntactically three classes of queries that admit constant update time and constant enumeration delay. We call such queries tractable. Depending on the class, the preprocessing time is linear, polynomial, or exponential (under data complexity, so the query size is constant). To decide whether a query is tractable, it does not suffice to analyse separately the sub-queries over the static relations and over the dynamic relations, respectively. Instead, we need to take the interaction between the static and the dynamic relations into account. Even when the sub-query over the dynamic relations is not tractable, the overall query can become tractable if the dynamic relations are sufficiently constrained by the static ones.