Efficiently Estimating Joining Cost of Subqueries in Regular Path Queries

Efficiently Joining Group Patterns in SPARQL Queries

In SPARQL, conjunctive queries are expressed by using shared variables across sets of triple patterns, also called basic graph patterns. Based on this characterization, basic graph patterns in a SPARQL query can be partitioned into groups of acyclic patterns that share exactly one variable, or star-shaped groups. We observe that the number of triples in a group is proportional to the number of ...

Cost-Based Optimization of Regular Path Queries on Large Graphs

The significance of regular path queries (RPQs) on graphlike data structures has grown steadily over the past decade. Prominent application areas are XML/XPath, RDF/SPARQL, analysis of social networks, and queries on biomedical networks. However, current implementations of RPQ are restricted either in the type of the graph (e.g., only trees), the type of regular expressions (e.g., only single s...

Universal Regular Path Queries

Given are a directed edge-labelled graph G with a distinguished node n0, and a regular expression P which may contain variables. We wish to compute all substitutions φ (of symbols for variables), together with all nodes n such that all paths n0 → n are in φ(P). We derive an algorithm for this problem using relational algebra, and show how it may be implemented in Prolog. The motivation for the ...

Preferential Regular Path Queries

In this paper, we introduce preferential regular path queries. These are regular path queries whose symbols are annotated with preference weights for “scaling” up or down the intrinsic importance of matching a symbol against a (semistructured) database edge label. Annotated regular path queries are expressed syntactically as annotated regular expressions. We interpret these expressions in a uni...

Solving Regular Path Queries