Re: [xml-dev] RE: Compelling use case for XML Catalogs?

[David Carlisle <davidc@nag.co.uk>]

On 13/06/2011 16:24, Costello, Roger L. wrote:

> XML Catalog only works if:
>
>      - you have pre-knowledge of exactly what URLs will
>        be present in the XML (XSLT, XSD, RNG, SVG, etc.)
>        documents that you receive/process
>
>       - the XML documents will always contain the correct
>         URL; there will never be any accidental or malicious
>         alteration of URLs
>
> Yes?

Not really.

A common (and probably original) scenario is that you have a certain 
numer of locally installed dtd and a catalog mapping their canonical, 
external, names to the local copies.

Your configuration (or physical lack of connectivity) means that 
reference to external dtd will, in general, fail (which is what you 
would want if you are paranoid) so using a catalog you can ensure that 
the only external dtd that get referenced are the ones that you want to 
allow.

As John says though, if the document has an internal subset then dtd 
validation tells you nothing about the document other than that it is or 
is not self consistent.

David



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