Rewriting of Regular Expressions and Regular Path Queries

Rewriting Extended Regular Expressions

We concider an extened algebra of regular events (languages) with intersection besides the usual operations. This algebra has the structure of a distributive lattice with monotonic operations; the latter property is crucial for some applications. We give a new complete Horn equational axiomatiztion of the algebra and develop some termrewriting techniques for constructing logical inferences of v...

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...

On the Optimization of Queries Containing Regular Path Expressions

One of the main characteristics of object-oriented database management systems is the explicit representation of relationships between objects. A simple example for a query addressing these relationships arises, if we assume the object types Company , and Division with the relationship has division from Company to Division. In this case a query might ask for the companies which have a division ...

Solving Regular Path Queries