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Re: XML Schema and Entities
- From: Eric van der Vlist <vdv@dyomedea.com>
- To: "Bullard, Claude L (Len)" <clbullar@ingr.com>,"xml-dev@lists.xml.org" <xml-dev@lists.xml.org>
- Date: Wed, 20 Jun 2001 18:24:24 +0200
"Bullard, Claude L (Len)" wrote:
>
> The XML Schema Primer is not very clear with respect to the
> use of entities in XML Schema. I realize the need to use
> the DTD and internal subset, the food chain of resolution
> prior to invoking the schema engine, the use of Group over
> parameter entities, but what is done with type="xsd:entities"
> or type="xsd:entity" in the XML Schema? I see the note about
> using them only in attributes, but still, there isn't an example
> that clarifies what they are good for in the Schema.
Part 2 is clearer about them [1]:
[1] http://www.w3.org/TR/xmlschema-2/#ENTITY
"[Definition:] ENTITY represents the ENTITY attribute type from [XML
1.0 (Second Edition)]. The ·value space· of ENTITY is the set of all
strings that ·match· the NCName production in [Namespaces in XML] and
have been declared as an unparsed entity in a document type definition.
The ·lexical space· of ENTITY is the set of all strings that ·match· the
NCName production in [Namespaces in XML]. The ·base type· of ENTITY is
NCName. "
They are therefore as good for W3C XML Schema as unparsed entities are
for DTDs :=) ...
Personally I have never seen them used except in Simon St.Laurent
"elements of style" (a book that I recommend not only for this example
;=) ) where he gives the following example that could be used with a W3C
XML Schema defining that the content attribute has a type "ENTITY":
<!DOCTYPE unparsed_image SYSTEM "unparsed_image.dtd" [
<!ENTITY myGif "mygif.gif" NDATA image_gif>
]>
<unparsed_image content="myGif"/>
Hope this helps.
Eric
> Len
> http://www.mp3.com/LenBullard
>
> Ekam sat.h, Vipraah bahudhaa vadanti.
> Daamyata. Datta. Dayadhvam.h
>
--
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http://dyomedea.com/formation/
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Eric van der Vlist http://xmlfr.org http://dyomedea.com
http://xsltunit.org http://4xt.org http://examplotron.org
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