title: OData version 2 and 3 differences
body: <p>OData protocol documentation (<a href="http://www.odata.org/documentation">http://www.odata.org/documentation</a>) describes two versions - 2 and 3.</p>
  
  <p>What are the core differences between two versions?</p>
  
  <p>Are both versions are supported by existing client libraries or version 2 is considered to be "legacy"?</p>
  
  <p>To rephrase - are version 2 clients compatible with version 3?</p>