OData/GData ... when REST isn't enough ?

Today a colleague introduced me to "OData" (Open Data - from Microsoft) which I immediately saw from Wikipedia has a competing protocol "GData" (Google Data).

Embarrassingly, I've never heard of either.   After reading the quick guides on both, it leaves me wondering ... "Why ...?"  Why another protocol?  Isn't REST enough ? And if you want something more complex then  SOAP or XMLRPC or a few million other protocols.   But I'm (fairly) sure these were not invented just to have another TLA ...

They both seem to leverage AtomPub ... but layer with their own structures.

So my question to the group is (Q0: is this the right group?)

Q) What is the purpose of these new protocols that existing protocols didn't solve ?

Q) Are people using these for anything except what the protocol developer teams developed ?

Q) This this make anything easier than other protocols ?

Thanks for any opinions ... I like to keep up to date on these kinds of things but it's hard to decide which to  spend more than 5 minutes on ... (I thought these very same things about XML at first ... sigh ... my tech predictor isn't so great).

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David A. Lee

dlee@calldei.com

http://www.xmlsh.org