-- pattern A ----------------
<element name="foo">
<data type="string">
<except>
<value type="string"/>
</except>
</data>
</element>
-----------------------------
matches to
<foo> </foo>
because according to the equality of the string type,
" " != "".
The above pattern doesn't match
<foo></foo>
because the content ("") matches to the except clause.
Therefore, this is not an equivalent of
-- pattern B ----------------
<element name="foo">
<data type="string">
<except>
<empty/>
</except>
</data>
</element>
-----------------------------
because this does NOT match <foo></foo>.
Now, consider
-- pattern C ----------------
<element name="foo">
<data type="string">
<except>
<value type="token"/>
</except>
</data>
</element>
-----------------------------
This does NOT match to
<foo> </foo>
because according to the equality of the token type,
" " == "" and therefore it matches to the except clause.
To summarize, here is the matrix:
A B C
<foo/> x x x
<foo> </foo> o x x
<foo>xyz</foo> o o o
o:valid x:invalid
regards,
--
Kohsuke KAWAGUCHI +1 650 786 0721
Sun Microsystems
