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Re: XSchema question

• From: "Don Park" <donpark@q...>
• To: <xml-dev@i...>
• Date: Tue, 4 Aug 1998 23:54:58 -0700

>If I understand you you want to have a schema/DTD that changes dynamically
>with time, driven by the contents of the (changing) document. This is not
>common in traditional SGML where the DTD is used to constrain documents to
>a pre-conceived format. Your approach is to review the contents of the log
>file and change the DTD/schema to reflect them. It isn't common to generate
>DTDs from documents but there is a tool called FRED from OCLC which
>apparently does this. Of course a human could also do it.

'dynamic-schema' is not driven by the contents but by the needs.  It is
somewhat similar to namespaces except with versions.  *sigh* I am not
explaining this too well, am I?

>XSchemas can be 'inline' in that being an XML document they can be included
>(using the entity mechanism:
>
><!DOCTYPE MyLog [
><!ENTITY myschema SYSTEM "myschema.xml">
>]>
><MyLog>
>&myschema;
>... rest of log file ...
></MyLog>


Above is 'inline-expansion' and not quite 'inline'.  'myschema.xml' exists
outside the document rather than being part of the stream.

'Inline-schema' looks similar to internal DTD subset except it can be any
where in the XML stream and not just in the !DOCTYPE declaration section at
the beginning of a XML stream.  'Dynamic-schema' is simply schema which can
be changed.  I don't know XSchema too well so allow me to use DTD syntax to
illustrate an exampe:

<schema>
    <!ELEMENT foo (a, b)>
</schema>
<foo>
    <a>
    <b>
</foo>
<schema>
    <!ELEMENT foo (a, c)>    <!-- redefine foo element's containment
rules -->
</schema>
<foo>
    <a><c>
</foo>

Am I being any clearer?

Don



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