[펌]Why RDF model is different from the XML model

막연히, RDF 가 더 간단하고, 머신 친화적(?) 이라고 알고 있다가,
문득 생각나 찾아봤다.
비슷한 질문을 수없이 들었다는 Tim 이 꽤 간단 명료하게 해설을 해놓았다.
관심이 있다면 꼭 읽어보기 바란다.
XML 는 구조가 다변적이고 의미가 애매해서 문제가 된단다. 원문에 예제들이 있다.
물론, 이것이 장점이 될수도 있겠지만  의미를 해석하는데는  한계가 있다.

Things you can do with RDF which you can't do with XML include

• You can parse the semantic tree, which end up giving you a set of (possibly mutually referential) triples and then you can use the ones you want ignoring the ones you don't understand.

Problems with basing you understanding on the structure include

• Without having gone to the trouble of getting the schema, or having an application hand-programmed to recognise a particular document type, you can't pick up any semantic information from a document;
• When an XML schema changes, it could typically introduce new intermediate elements (like "details" in the tree above or "div" is HTML). These may or may or may not invalidate any query which has been based on the structure of the document.
• If you haven't gone to the trouble of making a semantic model, then you may not have a well defined one. ( Look at a label on the jam jar which says: "Expires 1999". What expires: the label, or the jam? Here the ambiguity is between a statement about a statement about a document, and a statement about a document. )

Why RDF model is different from the XML model - Tim Berners-Lee