Re: Notation system ID

Subject: Re: Notation system ID
From: Chris Maden <crism@xxxxxxx>
Date: Wed, 27 Aug 1997 09:59:04 -0400
[Frank Christoph]
> I know what a notation is and I know what a system ID is.  What is a
> notation system ID, exactly?  More specifically, what is the
> appropriate thing to supply as a value for the external-graphic flow
> object's notation-system-id: property for a TIFF image?  Is it
> supposed to be a program that turns a TIFF image into whatever
> format the backend produces?

A good question.

This is, to me, one of the big weirdnesses of SGML.  Designed as a
portable document markup language, it then asks for a system
identifier for a format.  Is that a specification of the format for a
human to read?  Is it a processor?  Neither is very useful to an
automated process on another system.

However, since the birth of SGML, there has evolved the wonderful
concept of MIME types.  And, with the Extended Facilities Annex of
HyTime 2, I understand that <mimetype> (or something like it) is a
valid specifier for a Formal System Identifier.

I *strongly* recommend the use of MIME types as notation system
identifiers; facilities for resolving them into helper applications or
processing routines exist on nearly every system, and are increasingly
becoming part of operating systems.

A prime potential weakness of XML is its insistence that all system
identifiers by URLs - including notation system identifiers.

> Incidentally, since we are on the subject of IDs, where does one
> learn the _public_ IDs of things (like TIFF, for example)?  I seem
> to recall a seeing mention of a standard that lists such things, but
> is there an alternative resource?  (If not, a list of common public
> IDs --- for SGML, TIFF, GIF, TeX, etc. --- would be a useful
> addition to the DSSSL Handbook.)  I suppose not, since the
> registration needs to be centralized... sometimes I think it would
> be much better to work out some sort of system using public key
> encryption to decentralize registration mechanisms for URLs, domain
> names and the like.  <sigh>

DeRose & Durand's _Making Hypermedia Work_ included an appendix of
formal public identifiers for a lot of multimedia formats.  Kluwer is
the publisher, and it's available from Amazon.

<!ENTITY crism PUBLIC "-//O'Reilly//NONSGML Christopher R. Maden//EN"
"<URL> <TEL>+1.617.499.7487 <FAX>+1.617.661.1116
<USMAIL>90 Sherman Street, Cambridge, MA 02140 USA" NDATA SGML.Geek>

 DSSSList info and archive:

Current Thread