In this paper we address the problem of query rewriting in the context of semi-structured data. We present a method for computing the rewriting of a regular expression E in terms of other regular expressions. The method computes the exact rewriting (the one that defines the same regular language as E) if it exists, or the rewriting that defines the maximal language contained in the one defined ...

This document proposes an algebra for XML Query. The algebra has been submitted to the W3C XML Query Working Group. A novel feature of the algebra is the use of regular-expression types, similar in power to DTDs or XML Schemas, and closely related to Hasoya and Pierce’s work on Xduce. The iteration construct is based on the notion of a monad, and involves novel typing rules not encountered else...

We present specification languages that naturally capture exactly the regular and ω-regular properties that are stutter invariant. Our specification languages are variants of the classical regular expressions and of the core of PSL, a temporal logic, which is widely used in industry and which extends the classical linear-time temporal logic LTL by semi-extended regular expressions.

We give two constructions for semi-regular relative difference sets (RDSs) in groups whose order is not a prime power, where the order u of the forbidden subgroup is greater than 2. No such RDSs were previously known. We use examples from the first construction to produce semi-regular RDSs in groups whose order can contain more than two distinct prime factors. For u greater than 2 these are the...

The exchange and storage of XML data is becoming increasingly important. In contrast to conventional semistructured data 4, 1], the labels in a document-oriented representation such as XML are ordered. Furthermore, regular expressions (DTDs) describe the horizontal (and vertical) structure of the data. Traditional query languages for semi-structured data ignore the horizontal order and are ther...

We describe the isomorphism class of the torus centralizing a regular, semi-simple, stable conjugacy class in a simply-connected, semi-simple group. Let k be a field, and let G be a semi-simple, simply-connected algebraic group, which is quasi-split over k. The theory of semi-simple conjugacy classes in G is well understood, from work of Steinberg [S] and Kottwitz [K]. Any semi-simple conjugacy...