W3C home > Mailing lists > Public > w3c-sgml-wg@w3.org > February 1997

Re: SERIOUS concerns about implementation

From: Peter Murray-Rust <Peter@ursus.demon.co.uk>
Date: Thu, 20 Feb 1997 17:23:21 GMT
Message-Id: <3652@ursus.demon.co.uk>
To: w3c-sgml-wg@w3.org
In message <199702201642.LAA01649@www10.w3.org> Michael Sperberg-McQueen writes:
> On Thu, 20 Feb 1997 06:35:10 -0500 Peter Murray-Rust said:
[...  PM-R's  material deleted ...]

I said that I am prepared to accept communal discipline and I don't
intend to post further on this topic unless asked :-)

> I'm sorry to see members of the WG taken by surprise on this topic.

I got the impression from 2-3 mails that this had surprised people and 
I am sorry if I have raised an issue that had been put to bed.  

> I for one thought it was obvious long ago, and never hidden or
> disguised, that the restrictions on comments, entity types, content
> models, and attribute declarations would require the preparation of
> XML-compatible versions of standard entity sets from ISO and elsewhere,
> as well as of XML-compatible versions of standard DTDs like Docbook,
> TEI, and HTML.  So I'm neither surprised nor shocked by Peter
> Murray-Rust's discovery, though I am alarmed to see that some members of
> the WG seem surprised by it.

My reaction is that it will create a lot of work and potentially some
confusion.  Not everyone will initially understand the reason for two sets of
entity sets which differ only by asterisks and they may occasionally muddle
them up. If this is recognised and accepted, that's fine.

> The preparation of XML-compatible versions of these files is (a) not
> hard, and (b) something that need be done only once.  It seems to me a
> very small price indeed to pay for the simplifications we get in
> declaration syntax and entity handling.

I accept that for large well-financed organisations this isn't a problem.
Nor is it a problem for people who are developing a complete XML solution
without any reference to existing SGML.  The problem will hit those who
(like me) are on the fringes of the SGML community and who have to make
do with what bits and pieces they can pick up.  

My own position is that my DTD (CML) is (now) not interoperable with XML.
The problem is not primarily technical.  The components that CML interoperates
with belong to other organisations who own the copyright and for each of
which I shall have to get permission to alter and redistribute the material.
Whilst I am sure this will come in time, it's not something that a single
individual is likely to make much headway with.  Therefore, I cannot
legally distribute my material in XML-form (unless I have misunderstood
I will predict that what will happen is that people will develop XML software
which has switches on the command line, that allow it to read 'SGML' entity 
sets, rather than the confusion of interoperating with 'SGML' sets and 'XML'
sets in neighbouring directories.

> So, with respect, I suggest that any proposals to
>   - start allowing comments in arbitrary SGML declarations
>   - return to the use of -- -- com delimiters
>   - remove the restrictions on content models which will make many
>     existing DTDs break with XML parsers
>   - restore the SDATA entity type
> need some further motivation before we reopen these questions.  We knew
> when we made the original decision that existing SGML DTDs and entity
> sets use these constructs.  We knew that eliminating the constructs
> would mean making new XML-compatible versions of the files we all use.
> Nothing has changed.  Is there a reason to revisit the decisions?

No :-)  But it would be a useful thing for those of us who are trying to 
develop software to have the definitive XML versions of the common DTDs and 
entity sets.  At present my XML development is stalled until this happens.


Peter Murray-Rust, domestic net connection
Virtual School of Molecular Sciences
Received on Thursday, 20 February 1997 12:50:22 UTC

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