Question about default context node

[Alex]

Hi,

is a default context node part of the XQuery standard? I'm getting 
conflicting messages. For one, I heard statements that you need to use 
doc(), collection() or external variables to pass in data to an 
XQuery. On the other hand, implementations like Saxon provide methods 
like setContextNode() in their Java API so a simple XPath like /a/b/c 
is also a valid XQuery that makes sense. I like the context node 
option because of its simplicity but am not sure if it's standard. I 
haven't seen support for it in XQJ.

I would appreciate any clarification and references to the XQuery 
standard concerning context nodes set from the API.  

Thanks,
alex