Current applications export and exchange XML data on the web. Usually, XML
data are queried using keyword queries or using the standard structured
query language XQuery whose core consists of the navigational query
language XPath. In this context, one major challenge is the querying of the data
when the structure of the data sources is complex or not fully known to the
user.
Another challenge is the integration of multiple data sources that export
data with structural differences and irregularities. In order to deal
with these challenges, we consider a query language for XML which generalizes
and strictly contains Tree-Pattern Queries (TPQs) and can express a broad
structural fragment of XPath. Because of the expressive power and flexibility
of this language, processing and evaluating queries pose new problems.
In this presentation, we will discuss recent results with respect to these issues.