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RE: Why Are Schemas Hard?

• From: "Bullard, Claude L (Len)" <clbullar@i...>
• To: Don Park <donpark@d...>, 'xml-dev' <xml-dev@l...>
• Date: Thu, 23 Aug 2001 08:35:38 -0500

True and brought up several times during the discussions of 
relying on the well-formed paradigms.  Schemas are hard to read 
and so will any schema system designed around XML.  There is also 
the overload of ELEMENT elements and so on.   If a schema system 
is an XML application language, this is inevitable, but I agree.

After some practice with it, I find I can read them.  It took 
awhile to quit mentally translating them back into DTDs.  I also 
need the IDE, but not for reading.  Except for the automated 
diagrams, the *griddiness* takes practice.  What I need the IDE 
for is immediate sanity checks of the parsing, and to give me 
the drop down lists for facets, components, etc.  So far, 
personally, I like the XML Spy product, but when the beta dies 
I get to try another one so by the time I am done, I'll have a
fair idea of what works for me and what doesn't.  Sort of a DUH, 
but using the xsd:documentation elements everywhere helps a lot.

But the IDE for developing the schema without the rest of the 
puzzle of how one then uses the schema beyond validation, is 
incomplete.  At some point, I have to load up the .NET betas 
and find out how well the VisualStudio tools work.  

Part of the answer to the question is how good are the tools, 
but that is always an issue.  Schemas themselves, their validation 
power, their coherence with either data-centric (say relational) or 
OOPness seems to concern people the most.  I noted Alex's tool 
for taking Schema's and getting the initial C++ classes and commented 
the page needs more information about what the tool is for.  That 
is just document work.  When I review the output, he appears to 
have done an outstanding job of mapping.   That provides a sort 
of existence proof for one application of schemas.   Do others 
have reactions to that approach?

Len 
http://www.mp3.com/LenBullard

Ekam sat.h, Vipraah bahudhaa vadanti.
Daamyata. Datta. Dayadhvam.h


-----Original Message-----
From: Don Park [mailto:donpark@d...]
Sent: Wednesday, August 22, 2001 7:21 PM
To: 'xml-dev'
Subject: RE: Why Are Schemas Hard? (WAS RE: "Uh, what do I need this
for" (was RE: XML.COM: How I Learne d t o Love daBomb))


> 1.  What about Schemas is hard?

I think one important factor is the readability.  While DTD is arcane, I
find it more readable than XML Schema.  XML Schema is more verbose,
fragmented, and complex than DTD.  With a DTD file, I can see the structure
at a glance (as long as the author didn't go overboard with parameter
entities), but not so with XML Schema where structure is hidden in a jungle
of elements.  In this jungle, namespace declarations dangle like vines and
obstructs your view of the whole.  Visual tools helps but their GUI design
usually limits 'field-of-vision' to one object at a time.

I am sure there are other facets, but readability seems to be a key factor.

Best,

Don Park
Docuverse


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