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Re: Public Identifiers

• From: Paul Grosso <pgrosso@a...>
• To: xml-dev <xml-dev@l...>
• Date: Mon, 24 Jul 2000 11:27:15 -0500

At 16:08 2000 07 24 +0100, Leigh Dodds wrote:
>Is it legal to define my own Public Identifiers for document types?

Yes.

>I'm assuming it is, given that the first section of the identifier 
>allows me to indicate whether I'm a 'registered owner' or not
>(i.e. +//... versus -//...)

Correct.  The general format of a Formal Public Identifier (FPI) 
that you can define yourself (unregistered) for a DTD in English is:

  -//<owner identifier>//DTD <text description>//EN

where <owner identifier> is some string that identifies you (at 
least in your mind--there is nothing officially registered about
this), and <text description> is your very brief "description"
(more like "title") of your DTD.

Note that there are restrictions on what characters can go into
this string (see production 12 and 13 of the XML spec [1]).

There is nothing registered about the above, so you aren't really
guaranteed uniqueness, though a carefully chosen owner identifier
should help.

The WEB-SGML TC to ISO 8879 [2] defines a way to use an Internet Domain
Name as an owner identifier that allows you to define an FPI that is
considered "registered" (and hence starts with "+" instead of "-"): 

  +//IDN <internet domain name>//DTD <text description>//EN

where <internet domain name> is something like www.example.com.
So if you own (or have rights to use) a domain name, you can
create "registered" FPIs using the above.

Of course, public identifiers have to be resolved before they
can be used, so some kind of catalog support would be needed
in the tools you use (see, for example, [3] for more pointers 
about that).

paul

[1] http://www.w3.org/TR/REC-xml#NT-PubidLiteral 
[2] http://www.ornl.gov/sgml/wg8/document/1955.htm
[3] http://lists.xml.org/archives/xml-dev/200007/msg00241.html

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