GraphLog

TLDR

The paper introduces GraphLog, a graph‑based query language for data and queries, and outlines extensions for aggregates and path summarization. GraphLog encodes queries as graph patterns with edges or paths, using regular expressions to qualify paths, and is implemented in a prototype system. GraphLog’s expressive power matches stratified linear Datalog, first‑order logic with transitive closure, and nondeterministic logarithmic space—a previously unknown equivalence.

Abstract

We present a query language called GraphLog, based on a graph representation of both data and queries. Queries are graph patterns. Edges in queries represent edges or paths in the database. Regular expressions are used to qualify these paths. We characterize the expressive power of the language and show that it is equivalent to stratified linear Datalog, first order logic with transitive closure, and non-deterministic logarithmic space (assuming ordering on the domain). The fact that the latter three classes coincide was not previously known. We show how GraphLog can be extended to incorporate aggregates and path summarization, and describe briefly our current prototype implementation.