Extra Complexity?

[Paul Prescod]

"Samuel R. Blackburn" wrote:
> 
> It depends on how you use XML. If you use it to transfer
> data between applications then DTD's are completely useless.
> Their assumption that the world is flat is inappropriate for
> data applications. 

DTDs model tree structures.

> Also, the validations performed using DTD's
> don't buy you anything. The application must perform its own
> validation based upon some business rules. DTD's allow you
> to "validate" that a field contains a number but you can't use
> DTD's to "validate" that a field contains a prime number (that
> is an application layer validation).

So what you are saying is that because DTDs do not do everything you could
dream of, they should not be used for anything? A more effective point of
view is: "use DTDs for the 90% of the problem that they CAN solve, but
expect to require application-specific logic for the 10% that they
CANNOT." When "XML Schemas" come about, that number may shift to 95% and
5% but the basic principles will not. I'm fairly confident that there will
be no provision for validating that a number is prime, unless it is
through an "escape mechanism." DTDs also have an "escape mechanism".

 Paul Prescod  - ISOGEN Consulting Engineer speaking for only himself
 http://itrc.uwaterloo.ca/~papresco

"Remember, Ginger Rogers did everything that Fred Astaire did,
but she did it backwards and in high heels."
                                               --Faith Whittlesey

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