Make clear that SPARQL prefixed names are not CURIEs

A comment on the Last Call draft of SPARQL 1.1 Query 
http://www.w3.org/TR/2011/WD-sparql11-query-20110512/

If Section 4.1.1.1 “Prefixed Names” is read without prior knowledge of Turtle or XML, then a reasonable reader would have no idea that only a restricted set of characters is allowed in local names. The section can easily be read as allowing *any* IRI to be abbreviated using PREFIX.

It is documented that the editors of both HTML5 and Turtle made that mistake.

The potential for confusion is further increased by the fact that CURIEs in RDFa are virtually identical to prefixed names, except that they allow *all* characters.

Therefore I think it is important to draw attention to the syntactic restriction of local names in 4.1.1.1 (or perhaps somewhere near the example at the end of 4.1.1).

Something along these lines:

“Note: Most punctuation characters are disallowed in the local part of prefixed names. Therefore, @prefix and prefixed names are most useful for abbreviating class and property IRIs, which by design usually avoid such punctuation. Other IRIs, such as web links, can often only be written using the angle bracket syntax, either as absolute IRIs, or relative to the base IRI.”

Thanks,
Richard