XML vs RDF, An interesting debate on XMDR webpage..

After extensive discussion and investigation, we propose to use XML as both a data model and data exchange format for the XMDR Prototype. In addition to supporting the REST architectural style, this approach will greatly simplify both specification and development of an exemplar XMDR system. While we gave some consideration to using some less conventional representations (such as dialects of XMI and SCL), none seemed to have distinct advantages over the two major W3C formats: XML and RDF (W3C's Resource Description Framework). The exchange format is not for exchange between the registry and the sources of concept system (registry input), rather it is for exchange between the XMDR and clients. Concept systems may be received in the form of their native relational, hierarchical, or other data model. Internally, the XMDR may store the concept system in both its native data model, and the canonical XML data model.

for more details please visit http://hpcrd.lbl.gov/SDM/XMDR/arch/index.html