One of the requirements of current Semantic Web applications is to deal with heterogenous data. Data represented and stored using the Extensible Markup Language (XML) is almost ubiquitous and is the standard for data exchange. Resource Description Framework (RDF) is the W3C recommended standard for data representation. Being able to work with these two languages using a common framework is a great advantage and eliminates several unnecessary steps that are currently used when handling both formats.
A small presentation of XSPARQL in 5 slides is available.
XSPARQL has been published as a W3C member submission.