I thought it might be good to pick some of the low hanging fruit from
the issues page and see if we couldn't deal with them. The following
are all related to xmlns declarations:
Empty xmlns prefix -
http://www.rdfa.info/wiki/Rdfa-in-html-issues#Empty_xmlns_prefix
The Namespaces in XML Recommendation defines the syntax for the xmlns
attribute. That syntax does not permit an empty prefix name (e.g.
xmlns:="lala"). Therefore, such a declaration is invalid and would
never result in a prefix mapping being created in a conforming parser.
Underscore xmlns prefix
It is certainly legal xmlns syntax to declare a prefix mapping such as
xmlns:_="foo". However, such a mapping would collide with the internal
use of the reserved prefix name '_'. The RDFa Syntax Recommendation
does not specifically prohibit the explicit declaration of such a
prefix, but I think it probably should have. If the group is in
agreement, then I believe we can address this omission via the
specifications errata page. Specifically, the specification should say
something like "The CURIE prefix '_' is reserved for use by languages
that support RDF. Therefore, a prefix mapping for '_' MUST NOT be
declared in a source document, and conforming parsers MUST ignore any
such explicit prefix mapping."
I can't see any other way to address this issue in a way that would not
result in ambiguous interpretation of CURIE references that are prefixed
with '_'.
Colon in xmlns prefix
Again, as per the Namespaces in XML Recommendation, a colon is not
permitted in an xmlns prefix. It is therefore not permitted in a CURIE
prefix. Such a declaration is invalid and would never result in a
prefix mapping being created in a conforming parser.
Empty xmlns value
As per section 2.2 of the Namespaces in XML Recommendation, the empty
string cannot be used as a namespace name. This also means it cannot be
used in a prefix mapping in a CURIE. It is invalid, and the prefix
declaration should be ignored by a conforming parser.
And just to be clear, in the situation where there is no defined prefix
mapping for a prefix name used in a CURIE, that CURIE is ignored. So,
if I have a situation like <span xmlns:mine=""
property="mine:foo">test</span> no triple will arise out of this.
I do believe that it would make sense to ensure the test suite exercises
these edge cases. I have proposed some test cases (0127 , 0128) and
will propose more once we have reached consensus.
Comments?
--
Shane P. McCarron Phone: +1 763 786-8160 x120
Managing Director Fax: +1 763 786-8180
ApTest Minnesota Inet: sh...@aptest.com
