lee at sq.com lee at sq.com
Mon Mar 24 18:25:46 GMT 1997

> > Peter Murray-Rust wrote:
> I still don't know if there is a difference between 'GI' and 
> 'Element type', for example.

In XML they are the same, as far as I can tell.

The detailed reasoning follows, but you can ignore it if you like....



An element type can be a generic identifier, a name group,
a ranked element or a ranked group. [117; p. 406 of the SGML Handbook]

We don't have RANK in XML, so
An element type can be a generic identifier or a name group.

For example,
<!Element (boy|girl) (%child;)>
in SGML defines the content for both boy and girl.

This is (I think) not allowed in XML, so in XML there is no practical
difference between a GI and an element type.

See also the definition of a GI:

The idea seems to be that a generic identifier specification is used
to give in an instance the type of an element, once the parser has
determined that an element is beginning to happen.  The terminology
seems so obfuscatory to me that I see no benefit to the distinction for
SGML itself, let alone for XML, but maybe that is because I lack a legal
background :-)

If you have difficulty with some of the SGML terminology, also bear in
mind that (1) people who have been working with SGML for years also
have difficulty with it, (2) some of the WG8 people also seem to have
difficulty with it, and (3) I do not believe that there is 100% total
agrement on what it means even among the original SGML committee, at
least not at a technical nuts-and-bolts level.  The only consolation
is that HyTime terminology is far, far worse :-) :-)


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