Generalising XPath for Directed Graphs

XPath is a very natural and powerful way to specify locations in XML documents. This paper examines possible generalisations of XPath to allow both locations and paths through generalised labelled directed graphs to be specified. The need for such a path language is driven by work in querying Linguistic Annotations which are in general more complex in structure than XML documents. The result of this exercise is a powerful path language which reduces to XPath as a special case and which could potentially be useful in a range of query applications.

http://www.ics.mq.edu.au/~cassidy/papers/extreme03.html