Inside the increasing tornado of messages spinning in
unpredictable
directions on both XML-DEV and xml-uri@w3.org, we try and
take
a step backward and extricate the core facts and issues from
the
debate.
The discussion is clouded with the tangling of three
different layers of
discussion:
At a higher level, there is the semantic
web vision advocated by Tim
Berners-Lee: "the crucial thing is to recognize
that the namespace
identifier identifies the language of the message and so
indirectly its
meaning". This is opposed to a single focused view of
the usage of
namespaces strictly conforming to the Namespace
Recommendation, as voiced
by Jonathan
Robie: "to me, namespaces are used to disambiguate
names, and are
used in the process of tokenizing".
The next level is a debate around the legitimacy of using
namespace
URIs as pointers to XML Schemas, and an underlying
assumption
that XML
semantics should be carried exclusively through schemas.
This
option,
already used
by Microsoft tools is
not endorsed by the Schema WG, and
David
Cleary said:
The Schema WG is not advocating that
schemas be
pointed to by namespace
URIs. That is what the SchemaLocation attribute is for. Do
not confuse
the
opinions of some as the consensus of the Schema
WG.
The lower level is about the usage of relative URIs, and
is the starting point of the discussion--it would be a
purely theoretical point without the assumption than
namespaces could be
used as pointers. The
issue is not
new and James Clark gave evidence of
similar debates back in 1998 when
namespaces where still a Working Draft.
Several posts have proposed possible solutions to get out
of this loop:
Simon St.Laurent proposed
a "status quo" respecting a strict reading
of the recommendation together with some flexibility around
namespace
URIs usage: "by my reading, relative URIs are
permitted
in XML
namespaces, but namespaces will be compared as strings -
character for
character - not as converted to absolutes. Applications that
want to go
on from there could resolve and dereference the URI on their
own
recognizance, retrieving a schema, a package, a list of
lightbulb
jokes."
David Cleary proposed
to
separate the URIs from the schema binding:
"attributes of the form
xmlns-binding:namespace-prefix="associated-uri-reference"
would be taken as declaring that the
associated-uri-reference was
associate
with the namespace signified by the previously declared
namespace-prefix."
Meanwhile, Tim Berners-Lee and others stick
to the proposal of "absolutizing"
the URIs: "there is a body of thought that
absolutizing is right. And
some code. And some specs. The same applied to literal
comparison. The
difference is that is we settle for URIs not being URIs,
then RDF comes
down like a house of cards, wheras if we go for
absolutization then we
probably don't have any real documents which
fail."
The previous transition
plan proposed by
Berners-Lee got a
cool
reception from the xml-uri list:
"we are still (in the early
stages of) opening doors on the problem and its
implications. After such
unprecedented action as opening the xml-uri list for public
discussion,
the W3C hierarchy surely is not ready to go so soon for a
quick solution
along the path of (perceived) least resistance; is
it?". One may, as did Joe
Kesselman, wonder
how this will
end up: "is there any process by
which we'll decide that this list has reached closure, or
failed to do
so?"