Why RDF model is different from the XML model
"Why should I use RDF - why not just XML?". This has been a question which has been around ever since RDF started. At our reseller's workshop, there was a clear difference of view between those who wanted to query documents and those who wanted to extract the "meaning" in some form and query that. This is typical. I wrote this note in a frustrated attempt to explain what the RDF model was for those who though in terms of the XML model. I later listened to those who thought in terms of the XML model, and tried to writ it the other way around in another note. This note assumes that the XML data model in all its complexity, and the RDF syntax as in RDF Model and Syntax, in all its complexity. It doesn't try to map one directly onto the other -- it expresses the RDF model using XML.
Sometimes it seems there is a set of people for whom the semantic web is the only graph which they would consider, and another for whom the document tree (or graph if you include links) is all they would consider. But it is important to recognise the difference.