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RE: TAG scheme - some comments

From: Hammond, Tony <T.Hammond@nature.com>
Date: Thu, 21 Oct 2004 14:13:17 +0100
Message-ID: <125F7834E11A5741A7D79412EE3504F90CE55A4A@UK1APPS2.nature.com>
To: 'Sandro Hawke' <sandro@w3.org>, "Hammond, Tony" <T.Hammond@nature.com>
Cc: uri@w3.org

> What 
> application for tags do you have in mind where parsing the 
> authorityName is necessary?

Simply that a TAG processor should be able to recognize a given URI to be a
TAG URI against the published syntax. Otherwise why both publishing a
syntax, anyway? Seems to me that you either want to generalize your
productions to include the possibility of a more generoc authoriyName oe
else dispense with the productions and leave it to the scheme alone to
declare that it's a TAG URI. ;)

I just don't believe you can leave the door open this way.

I'm also not a little sceptical about the following injunction:

> for generation only -- software SHOULD NOT parse tags.

The TAG has been minted to a specification which defines the two component
parts of a taggingEntity quite clearly: authorityName and date. I don't
believe there should be any problem in an application retrieving these
pieces of information.

This gets us back towards the opacity of URIs argument which confuses two
separate things - the URI string itself and the dereferent (aka
representation). URI strings are _not_ fully opaque but have at least a high
level generic structure and sometimes a more specific scheme structure or
sometimes even an application-level structure (e.g. OpenURL). An HTTP
processor must necessarily parse an HTTP URI to dereference it. In
particular, it can pick out a network authority, a path, etc. Likewise the
TAG scheme publishes a component architecture.


> -----Original Message-----
> From: sandro@roke.hawke.org [mailto:sandro@roke.hawke.org] On 
> Behalf Of Sandro Hawke
> Sent: 21 October 2004 13:58
> To: Hammond, Tony
> Cc: uri@w3.org
> Subject: Re: TAG scheme - some comments 
> After a quick two reads, your comments seems good/valid, thanks.
> Except this one:
> > 5. Sect 2.1 (para "Authority names...") and Sect. 4 ("There is a 
> > significant possibility...").
> > 
> > I do not see how one can issue a syntax and then require TAG 
> > processors to ignore that syntax in order to futureproof the spec. 
> > That is the statements
> > 
> > 	"To allow for such developments, software that 
> processes tags MUST 
> > NOT reject them on the grounds that they are outside the syntax for 
> > authorityNamde defined above."
> > 
> > 	"As stated in Section 2, however, to allow for future 
> expansion, 
> > software MUST NOT reject tags which do not conform to the syntax 
> > specified in Section 2."
> > 
> > IMO would appear to invalidate the utility of the spec. The way to 
> > deal with this situation is presumably to reissue a new TAG spec at 
> > such time as TAG processors have widespread support for alternative 
> > authority names.
> Why is this a problem?  We tell software how to mint tags to 
> avoid collisions; we tell software how to compare tags.  
> Those are the only things we expect people to do with tags 
> for which they might be different from other URIs.  Some 
> people might be inclined to try to parse tags - for some 
> application-specific reason - and that's okay, as long as 
> they obey the restriction you're challenging, that they don't 
> complain if they can't parse the authorityName.  What 
> application for tags do you have in mind where parsing the 
> authorityName is necessary?
> Maybe we need to state more clearly, near the BNF, that the syntax is
> for generation only -- software SHOULD NOT parse tags.   (This is
> wildly ironic, since I'm such a proponent of automated use of 
> grammars for both generation and parsing.  :-).
>      -- sando

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Received on Thursday, 21 October 2004 15:48:32 UTC

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