Blank nodes in queries and variables

Hi,

After fixing the remaining obvious bugs in the test-cases my Prolog parser
now has 100% coverage on the syntax.  Time for semantics ...

Just a brief question for my understanding. Is the following true? If
not, please explain why ...

	Variables (?name) and blank nodes (_:name) in queries are
	closely related.  The name-spaces for variables and blank nodes
	are not related (i.e. ?a is not related to _:a).  Blank nodes
	do not appear in the result-set of SELECT *.  Where a variable
	matches any resource or literal, blank nodes only match resources.

Notably the latter is unclear as -if I recall well-, the SPARQL document
anticipates on allowing literals as subject in the future.  Comments?

I suggest to add a paragraph to the SPARQL definition explaining the
relation between blank nodes and variables.

	Cheers --- Jan

P.s.	Ask if you want the diff between the original (XML) testcases
	and the fixed.