Querying Linked XML Document Networks in the Web
The W3C XML Linking Language (XLink) provides a powerful means for interlinking XML documents all over the world. From the database (and in general, querying) point of view, elements with linking semantics as specified by XLink can be seen as embedded views in an XML instance. Compared with classical databases, i.e., SQL and relational data, the situation of having links inside the data is new, raising new aspects for query languages: for using such documents, strategies how to handle links are required. There is not yet an official proposal on the interaction of interlinked XML documents using the XLink language and navigation/querying. We investigate a model where interlinked documents are regarded as virtual XML subtrees, i.e., XML views. Several strategies are presented how to handle such subtrees, concerning the timepoint when the link is evaluated, and the evaluation and caching strategies. The evaluation strategies are influenced by capabilities of the linked XML servers. So far, the approach is independent from the actual querying language. The approach is under implementation as an extension of LoPiX, a web-aware system for XML data manipulation.