It has been designed by a working party with representatives from Sun, Microsoft and Fujitsu, and influenced by established hypermedia technologies such as HyTime and Dexter. XLink links are expressed as sets of XML tags, and come in two types, simple and extended.
Extended links have a more complex structure, and support inbound and third-party links.
A third-party link allows information from multiple resources, such as a student's subjects, grades and personal details, to be brought together, again without the need to modify the remote sources' content. In effect, third-party links build virtual database records from heterogeneous sources, and documents containing collections of them are called, appropriately, 'Linkbases'. Both languages are due to enter their proposed recommendation stage in early October, and in the meantime the W3C is encouraging trial implementations, feedback and comment.