Re: Associating schema with document

[James Clark <jjc@jclark.com>]

> However, if I
> care compatibility, I still prefer to embed internal DTD subsets rather
> than a PI or attribute.  Does use of PIs or attributes have any
> advantages  over use of internal subsets?

Internal subsets don't support namespaces properly.

Internal subsets can be quite unwieldly if you have large DTDs 
(particularly if you have small instances).  The size of the internal 
subset may dwarf the size of the instance.  You can of course include 
declarations for just the elements used in the instance, but then you have 
a maintenance problem: every time you add a new element you need to check 
whether you need to add declarations.

There's also a fundamental difference: instead of having the schema in one 
place and referencing it, you are duplicating the schema information in 
multiple places.  If you change the RELAX NG schema (for example, by adding 
a new default attribute), the internal subset derived from it won't 
automatically change, whereas if you used a PI, then you wouldn't have to 
change anything if you changed the schema.

James