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Update on namespaces

From: Jon Bosak <Jon.Bosak@Eng.Sun.COM>
Date: Mon, 9 Jun 1997 23:06:00 -0700
Message-Id: <199706100606.XAA08152@boethius.eng.sun.com>
To: w3c-sgml-wg@w3.org
In order to better understand the requirements for namespaces, several
members of the SGML ERB met in phone conference with key participants
in the PICS-NG effort last Friday.  We didn't get through all the
issues in the time available, but we did arrive at some important
preliminary understandings.  There seemed to be general agreement on
the following:

1. One workable way to universally disambiguate the names of elements
is to associate them somehow with specific URIs.  Not everyone agrees
that this is the best way -- some of us would prefer a mechanism like
the SGML formal public identifier -- but there seems to be a general
acknowledgement that it will work.

2. While some namespaces may be specified in a machine-interpretable
form, other namespaces (and perhaps a certain component of all
namespaces) will be in a form that cannot be interpreted by a machine.

3. There seemed to be general agreement that validatable structural
information is not among the things that minimally need to be conveyed
by a namespace identifier.  For example, it might be necessary to
convey the information that an <author> element is intended to contain
the name of a human or organization that created a work, and it might
be necessary to convey the fact that its data type is STRING, but it
is not necessary in meeting the PICS-NG requirements that the <author>
element specify either an inherited content model from some DTD or
that it conform to a content model from some DTD.  In other words, as
far as we can tell at the moment, the namespace problem does not
require a solution that involves DTDs.  This does not mean that such a
solution would not be useful, but it does seem to imply that it can
wait for the SGML revision.

4. As indicated in the example just given, it is necessary to be able
to get more than one category of "meaning" about a given element.
These different semantic axes may have to come from different places.
For example, in <birthday>19850527</birthday> it may be necessary to
point to one specification in order to indicate that the content
refers to someone's date of birth and to a different specification to
indicate that content happens in this case to be in ISO format.  This
is multiple inheritance, but of a kind that can apparently be dealt
with simply by providing the ability to attach multiple namespace
identifiers to a given element.

5. There is hope that the additions to xml-lang needed in the short
term can be reasonably small, just enough to enable the solution of
the more general problem later on.

Received on Tuesday, 10 June 1997 03:21:26 UTC

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