XML trade off 1 - DTD vs XML Schema

[MEdson at walldata.com]

So do you believe that both DTDs and XML Schemas are necessary?  Would you
please elaborate on what advantage DTDs have over Schemas and if possible
explain why DTDs were NOT designed to be written in XML?

> -----Original Message-----
> From:	DuCharme, Robert [SMTP:DuCharmR at moodys.com]
> Sent:	Wednesday, July 21, 1999 9:53 AM
> To:	'XML Dev'
> Subject:	RE: XML trade off 1 - DTD vs XML Schema
> 
> >I challenge anyone to translate an XML Schema to a mental
> >model without the aid of either paper or machine. 
> 
> I'll go with the machine, since I have one on my desk, and it has lots of
> software on it capable of reading and manipulating XML documents. 
> 
> When XMI came out, I had just been studying up on UML, and I thought
> "Cool!
> I'll print out the DTD so that I can look it over on the subway ride
> home!"
> When I saw how big the XMI DTD was, I decided not to print it out--I
> prefer
> not to spend that much time in the subway. My point is that many XML 1.0
> DTDs are too big to form mental models of as well (especially when they
> use
> lots of parameter entities), but they're still useful in serious
> production
> environments, and schema that can't be understood by a visual skimming
> will
> still have a lot going for them. The added machine-readability of schemas
> has many system development payoffs, not least of which is that it will be
> more extensible than SGML-style declarations--once it's in place, adding
> new
> features to it will be easier than adding them to XML 1.0 DTD syntax.
> 
> It's adding up to having all the makings of a religious issue, which is
> too
> bad, because two years from now people will be getting work done using
> both
> styles. Each will be more appropriate for certain kinds of projects. 
> 
> Bob DuCharme          www.snee.com/bob           <bob@  
> snee.com>  "The elements be kind to thee, and make thy
> spirits all of comfort!" Anthony and Cleopatra, III ii
> 
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