Re: XHTML Working Draft--URLs for system ids of char entity decls

Paul Grosso <pgrosso@arbortext.com> writes:
> 
> In the latest XHTML DTDs [1], the external entity declarations used to
> reference the "Character mnemonic entities", e.g.:
> 
> <!ENTITY % HTMLlat1 PUBLIC
>    "-//W3C//ENTITIES Latin1//EN//HTML"
>    "HTMLlat1x.ent">
> %HTMLlat1;
> 
> have relative system identifiers (e.g., "HTMLlat1x.ent").
> 
> While this usually works if the processor knows how to canonicalize
> relative paths properly and the desired files are in the proper location
> relative to the DTD file, this seems unnecessarily fragile for such an
> important DTD.  Given that the WWW is pretty much based on URLs for
> accessing things, it seems that making these absolute, e.g.:
> 
>   http://www.w3.org/TR/WD-html-in-xml/DTD/HTMLlat1x.ent
> 
> might make sense.  This is, after all, from where the authoritative
> copies must be gotten in the first place. 

Paul,

This was discussed at some length, and the decision to not use absolute
URIs was made for two reasons:

   1. Because the XML Recommendation does not specify whether the 
      publicId or systemId has precedence, there was concern that
      if XHTML authors were to simply use the URL as provided (which
      I believe the vast majority would do), there may be an 
      unnecessary and draining load on the W3C http server each 
      time an XHTML document is validated. This may be considered
      a more fragile situation than providing a relative URL.
      
   2. Providing an absolute URI might indicate that documents not
      using the provided one were somehow not conformant, 
      unintentionally canonicalizing the URI itself in the spec.

I believe it better to advocate that authors and others keep a 
copy of the DTD in the same directory as the document, and if
they wish to put it in a different directory in their environment,
that they modify their DOCTYPE's URIs to point to that new location.
Or use a catalog file (which is what I'd recommend if XML had them
in the spec).
      
I don't think this is a great solution, but it seems that the 
alternative might be worse, especially if the W3C server was hit 
ceaselessly by each opening XHTML document. And I don't think W3C 
is attempting to become the DNS of DTDs here...   

Murray

...........................................................................
Murray Altheim, SGML Grease Monkey         <mailto:altheim&#64;eng.sun.com>
Member of Technical Staff, Tools Development & Support
Sun Microsystems, 901 San Antonio Rd., UMPK17-102, Palo Alto, CA 94303-4900

              An SGML declaration does not an i18n make.

Received on Monday, 22 March 1999 18:52:59 UTC