XML Schema Vs XML DTDs

[DW Emory <danemory@xxxxxxxxxxxxxxxxxx>]

It's my understanding that even the latest version of FM does not support 
XML Schemas, and there is little likelihood that future versions of FM will 
support them either.

XML Schemas were invented to enforce database schema requirements which 
cannot be enforced by a DTD. This strongly suggests that, when developing 
XML applications, best practice would dictate the use of an XML Schema 
rather than a DTD, even if, at least initially, a DTD will suffice. That's 
because you never know what changes in the database schema may occur in the 
future. If you implement at the outset with an XML Schema, you can easily 
modify it to track subsequent changes in the database schema. But if you 
implemented with a DTD, there is a constant danger you'll find yourself in 
a cul-de-sac

The reason for that conclusion can be confirmed by reviewing the following 
documents:

http://www.w3.org/TR/xmlschema-0/

http://www.brics.dk/~amoeller/XML/schemas/dtd-problems.html

When you examine the limitations of DTDs described in the second document 
you can see that a DTD-conformant document may not correspond with the more 
demanding requirements of the schema for the database in which that 
document is to be stored. This strongly suggests that your documents should 
conform to an XML Schema that can track the evolution of the database schema.

Suppose, for instance, that the database schema imposes certain 
restrictions on the values (or length) of a String-type attribute. That 
restriction would be enforced if the document were authored using an XML 
schema. But if the document were authored in accordance with a DTD, the 
document will pass the FrameMaker validation check, yet, when that document 
is exported as XML for inclusion in a database that enforces those 
restrictions, it will  be detected as invalid by the database even though 
it fully conforms to the DTD.

I await rebuttals and/or hand-wringing.





.
FrameMaker/FrameMaker+SGML Document Design & Database Publishing
DW Emory <danemory@xxxxxxxxxxxxxxxxxx>


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