W3C home > Mailing lists > Public > xml-uri@w3.org > May 2000

Re: Namespace names: a semi-serious proposal

From: Tim Berners-Lee <timbl@w3.org>
Date: Sat, 27 May 2000 08:50:11 -0400
Message-ID: <006801bfc7da$1b48b150$a60a1712@col.w3.org>
To: <abrahams@acm.org>, <xml-uri@w3.org>


Let's pop the stack - while it is useful to have shared context about
URIs and what they can do, and this list may be a way to get it, the
most essential point is that XML does not need to specify anything
about particular schemes.

The reason for using a URI is that you
_separate_ the design issues associated with any particular URI
scheme from the design of the language.   In other words,
discussions like these are broken into two parts: the design of the
language in terms of URIs, and the design of the URI schemes.
Temping though it is for the users of URI schemes to redesign XML
(how many non-xml languages have come out of the IETF recently?)
and the users of XML to redesign URIs,  this reduces the power and
resilience of the whole system.  This is one of the basic reasons
for my asking the XML designers to make it a URI pure and simple.

[This is independent of the relative URI debate now, we are talking about
the properties if the absolutized thing]

This is software engineering principle of modularity.

<analogy>The design of a towing hitch separates the design of car and
trailer.
While the designers of trailers discuss the number of cylinders a car
should have, and the designers of cars discuss whether trailers should
be made of fiberglass or aluminum, then nothing is ever settled.
Once a car can provide, and trailer accept, a standard hitch then the
customer
can make workable system with a big enough car and a stable enough
trailer for the job at hand.</analogy>

For an application which defines social expectations, then it may be
reasonable
to mandate particular uses of URIs.  The Platform for Privacy preferences,
for
example, states as part of the protocol that a URI given to a privacy policy
must
never ever used for anything else but exactly that policy.  But in the
general language
at a level as fundamental as the namespace spec, you can't presume the
social
conditions of an application. Just quote the URI spec.


Tim BL

(comments on the original message included below)

-----Original Message-----
From: Paul W. Abrahams <abrahams@valinet.com>
To: xml-uri@w3.org <xml-uri@w3.org>
Date: Friday, May 26, 2000 1:48 PM
Subject: Namespace names: a semi-serious proposal


>OK, the folks who brought the namespace spec into the world
>are of one voice: namespace names don't mean anything.  They
>are just unique identifiers.


(For those folks who had planned on society using the things,
this is rather a disappointment.  But perhaps it is as well,
as others say XML documents don't mean anything either ;-)

One wonders, if they mean nothing, why do they have to be unique?
Perhaps they should be replaced by empty strings!
Obviously they do have *some* meaning. They have a meaning because  their
identity properties allow information to be communicated about them. All
sorts of information - in specs,
schemas, corridor gossip, etc.  Once you identify something, then in fact
you can't stop people talking about it.

>So let's make the connotation match the denotation.  Let W3C
>set up a website that dispenses unique integers to all
>comers, no matter how nefarious or trivial their purpose.
>You ask for one and you get one.  Service on the spot, no
>questions asked.   In fact, you can get 10**12 of them at a
>shot if you wish.   As far as I know there is no imminent
>shortage of integers, though for the sake of ecology we
>might wish to use the Base64 notation or hexadecimal instead
>of decimal.


(We don't do this as a central repository, as we know that
being a central repository, while lucrative, prevents the web from scaling
and is socially unacceptable.

However, fo those doing W3C work, we happily do provide a persistent
URI of the form http://www.w3.org/YYYY/xxxxxx
where the YYYY is just a device to help us ensure there is no reuse.)

>The value of the xmlns attribute, i.e., the namespace name,
>is then a unique integer, obtained from the source from
>which such blessings flow.  The creator of the namespace can
>decide if a new version is sufficiently similar to a
>previous one to warrant a new number.

This is exactly the sort of author control of persistence which
the owner of an HTTP name has, in fact.

> It then is
>abundantly clear that a namespace name conveys no
>information whatsoever.


Alas, I will use the number to say something about it -- maybe even in
a standard - and then, it will have some meaning to anyone whohas read the
standard.

>In fact, there's no need even to restrict the dispensation
>of unique integers to a single source.  Anyone can get into
>the business as long as they themselves get a unique integer
>as their business card, and prefix the integers they
>dispense with their own ID and some appropriate delimiter.
>Any cad who sends the same integer to two people will
>deserve the same fate as that old Monty Python character who
>distributed fake Hungarian-English lexicons to Hungarian
>tourists in London.
>
>Maybe the integer dispenser already exists.  If it doesn't,
>it should.  It obviously has many uses.


There are as people have pointed out, many similar schemes
which have siilar properties.




Tim BL



>Paul Abrahams
>
>
Received on Saturday, 27 May 2000 08:48:56 UTC

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