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Re: XML Schema and Entities

"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.


> Len
> http://www.mp3.com/LenBullard
> Ekam sat.h, Vipraah bahudhaa vadanti.
> Daamyata. Datta. Dayadhvam.h
Pour y voir plus clair dans la nebuleuse XML...
Eric van der Vlist       http://xmlfr.org            http://dyomedea.com
http://xsltunit.org      http://4xt.org           http://examplotron.org