A Lock-Based Protocol for XML Metadata Knowledge Bases

Enhancing transactional performance for XML metadata knowledge bases (XMKBs) is crucial, as XML is widely used to describe metadata in knowledge bases for data integration. In XMKBs, XML elements, attributes, and texts illustrate knowledge entities´ types and contents, while the parent/child and ID/IDREF(s) relationships state the associations among knowledge entities. XML documents in XMKBs exhibit graphical structures, and yield knowledge entities which can be accessed via multiple paths. Several XML concurrency control protocols have been proposed for accessing XML documents. However, they treat XML documents as trees with no regard to the ID/IDREF(s) relationships used in the documents. These existing protocols are thus not applicable to XMKBs. In this paper, a new XML concurrency control protocol, namely XMP, is proposed for XMKBs. The novel feature of XMP is to model XML documents as XML graphs, where both graphical structures and operation access behaviors in XMKBs are considered. Our simulation results show the high concurrency of XMP.