Re: [xml-dev] Build Rich Complexity from a Small Set of Well-DefinedMark

[Philip Fearon <pgfearo@googlemail.com>]

Interesting. Do substitution groups count as an attribute combinator
then, rather than a markup combinator?

Phil Fearon
http://qutoric.com

On Wed, Aug 24, 2011 at 3:16 PM, Costello, Roger L. <costello@mitre.org> wrote:
> Hi Folks,
>
> Consider the digits 0 - 9. They can be combined to create an infinite number of integral numbers, such as 256 or 14 or 190023156001200021345. Each digit has a well-defined meaning and the rules for combining the digits are well-defined.
>
> Rich complexity flows from a small set of digit combinators.
>
> Next, consider XML Schema. It is a markup language consisting of a small set of well-defined markup combinators:
>
>    1.  Schema
>    2.  Element
>    3.  Attribute
>    4.  Simple Type
>    5.  Complex Type
>    6.  Attribute Group
>    7.  Element Group
>
> The language has well-defined mechanisms for combining the markup combinators:
>
>    1.  Schemas are combined using import, include, and redefine
>    2.  Elements are combined using sequence, choice, or all
>    3.  Complex types with simple content are extended or restricted
>    4.  Complex types with complex content are extended or restricted
>
> An infinite variety of schemas can be created using the 7 markup combinators and the 4 combining mechanisms.
>
> Interestingly, XML Schemas is considered to be a complicated language. Perhaps 7 markup combinators are too many in a markup language?
>
> When creating an XML markup language consider following this approach:
>
>    1.  Create a small set of well-defined markup combinators. From experience with XML Schemas, 7 or less markup combinators might be adequate.
>    2.  Create well-defined mechanisms for combining the markup combinators. Again, from experience with XML Schemas, 4 or less combining mechanisms might be adequate.
>
> From that will flow complexity of great richness.
>
> Comments?
>
> /Roger
>
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