- From: Andrew Layman <andrewl@microsoft.com>
- Date: Tue, 10 Jun 1997 08:33:44 -0700
- To: w3c-sgml-wg@w3.org
In a recent summarizing mail regarding namespaces, John Bosak said:
"... 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."
The phrasing in the last sentance is misleading. Setting the issue of
namespaces aside for a moment, the birthday example indicates that we
sometimes want to simultaneously specify the semantic meaning of an
element (i.e. "birthday") and also its notation (e.g. "Date-ISO-8061").
This could be accomplished by attaching multiple identifiers to an
element, as in '<birthday type="date">19850527</birthday>'. Tim Bray
made a proposal along these lines a month ago.
Where namespaces come in is that key terms in that example ("birthday,"
"type," and "date") have no universal meaning. As XML stands today,
their meaning is relative to the particular doctype and application
used. Namespaces is a facility to pin down names exactly, in effect
saying "'birthday' as defined by organization x, 'type' as defined by
w3c, 'date' as defined by w3c."
A more precise phrasing is "...the ability to attach multiple
identifiers to a given element (possibly from multiple namespaces)."
--Andrew Layman
AndrewL@microsoft.com
Received on Tuesday, 10 June 1997 11:33:54 UTC