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Re: When is an XML vocabulary too complex? The art and science

• From: Jim Melton <jim.melton@oracle.com>
• To: "Costello, Roger L." <costello@mitre.org>
• Date: Sat, 25 Feb 2012 13:01:10 -0700

Roger, I'm sure this reply won't really be helpful, but it's worth mentioning.

I don't recall to whom the statement is usually attributed, but "Make 
things as simple as they need to be, but no more" is good 
advice.  The real world is complex and modeling some fragment of it 
in XML requires understanding how faithfully and fully the model must 
represent the fragment of the real world.  If you're modeling a large 
corporation, you can make your model (in this case, your schema) far 
too complex if you insist on modeling the entire family trees of your 
employees and customers, along with details of their private lives -- 
none of which is relevant to the part of the world you *need* to have 
modeled; you can also make your model far too simple if you fail to 
address topics such as pensions, health care, physical addresses, job 
assignments, and the like.

Size and complexity are adjectives that describe two dimensions of 
models/vocabularies.  Good/bad is a different dimension.  That latter 
dimension is mostly orthogonal to the others.

Jim

At 2/25/2012 12:42 PM, Costello, Roger L. wrote:
>Hi Folks,
>
>If an XML vocabulary is large and complex, does that mean it's bad?
>
>Calculus is a large and complex field of mathematics, does that mean 
>Calculus is bad? Obviously not.
>
>........
>
>I am reviewing a large and complex XML vocabulary.
>
>Actually, I superficially reviewed it a few years ago and came to 
>the judgment, "This is too complex, it's no good."
>
>Now I am patiently reviewing it in depth.
>
>The vocabulary has a lot of optional elements and attributes, so I 
>am focusing on just the mandatory stuff and getting a firm 
>understanding of it.
>
>Gradually, as the need arises, I will pick up the optional stuff.
>
>I've noticed that many Calculus books introduce the core concepts 
>first and then describe the "non-core concepts" in later chapters. 
>Presumably that makes it easier to learn Calculus.
>
>Is optionality in XML vocabularies the markup equivalent of 
>"non-core concepts" in textbooks?
>
>In August there will be a conference on "What is Good XML?"
>
>Perhaps a characteristic of "good XML" is the frequent employment of 
>optionality in elements and attributes?
>
>..........
>
>Calculus is very useful. It's used in everything from calculating 
>the motion of planets to building bridges.
>
>But if all Calculus textbooks were written in a way that nobody 
>could understand then I suspect that it wouldn't matter how useful 
>Calculus is, it wouldn't be used.
>
>..........
>
>You may create the world's most useful XML vocabulary.
>
>But if nobody can understand it and teachers can't explain it then 
>it won't be used.
>
>So, the design of an XML vocabulary involves more than usage. It 
>also involves education and elucidation. Without the latter two, the 
>former is for naught.
>
>Using optionality as a means of expressing "Hey, this is non-core 
>information. You can learn it later if you need it" seems to be 
>fundamental to the art and science of creating large, complex vocabularies.
>
>What do you think?
>
>/Roger
>
>
>
>
>
>
>
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========================================================================
Jim Melton --- Editor of ISO/IEC 9075-* (SQL)     Phone: +1.801.942.0144
   Chair, ISO/IEC JTC1/SC32 and W3C XML Query WG    Fax : +1.801.942.3345
Oracle Corporation        Oracle Email: jim dot melton at oracle dot com
1930 Viscounti Drive      Alternate email: jim dot melton at acm dot org
Sandy, UT 84093-1063 USA  Personal email: SheltieJim at xmission dot com
========================================================================
=  Facts are facts.   But any opinions expressed are the opinions      =
=  only of myself and may or may not reflect the opinions of anybody   =
=  else with whom I may or may not have discussed the issues at hand.  =
========================================================================  

• References:
  • When is an XML vocabulary too complex? The art and science ofcreating large, complex vocabularies that are amenable to teaching,learning, and using.
    • From: "Costello, Roger L." <costello@mitre.org>