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At 11:52 06/06/2004, Elliotte Rusty Harold wrote:
>This is one of two qualitative differences between SGML and XML. In XML
>validity is optional. It is *not* required. Adding a document type
>declaration makes no promises that the document is valid. It simply says
>you might find this DTD to be useful when processing the document.
>Many developers believe that rigid, conservative (everything not permitted
>is forbidden) schemas are necessary to produce software. Nothing could be
>further from the truth. Programming with the expectation that the schema
>will be followed leads to brittle, inextensible, closed systems that break
>at the first whiff of change. Robust, flexible software that can handle
>extensions gracefully begins with the realization that any fixed schema is
>inadequate for some uses, and that one must be prepared to handle both
>schemaless and invalid documents.
What processing expectation should we have for such 'extensions' Elliotte?
Its foreign to an expected schema, not previously met... What is
your definition of robust and flexible? What one might call robust
and flexible, others might call guesswork?
>Sometimes the answer, is "I don't know" and the document may need to be
>kicked to a human for further analysis.
Which some might equate to 'fall over and die'?
I think the SGML world got it right on this one.