> btw .. are there some limitations on selector names?

so i think we have been there:
http://www.day.com/specs/jcr/2.0/6_Query.html#6.7.3%20Selector says a
selectorName is a Name.
http://www.day.com/specs/jcr/2.0/6_Query.html#6.7.4%20Name says a Name
is a JCR Name. if it is a legal sql name (so no ":") it can be unquoted,
otherwise it needs to be quoted. i verified with jackrabbit that this is
a valid query that yields a result:

    SELECT tags
    FROM [nt:unstructured] AS [nt:unstructured]
    WHERE tags = "foo" AND tags="bar"