Typing XPath Subexpressions With Respect to an XML Schema
This paper discusses typing XPath sub-expressions with respect to an XML schema, which is a new static analysis problem of XPath expressions. More formally, the typing problem is to decide whether there exists an XML document conforming to a given XML schema such that the nodes of the document matching to given sub-expressions of a given XPath expression are of the given types. Deciding this problem is useful for query rewriting induced by schema evolution or integration. The contribution of this paper includes a decision algorithm for the typing problem, provided that XPath expressions include no path union operator.