7 Questions on DCDs

Roger L. Costello costello at mail11.mitre.org
Tue Jan 12 16:11:36 GMT 1999


(1) Will a DCD have a DOCTYPE declaration, or is that a thing 
of the past?  

(2) XML instance documents will specify the the DCD it is 
conforming to using namespaces, rather the using the DOCTYPE
declaration?

i.e., instead of:

<?xml version="1.0"?>
<!DOCTYPE BookCatalogue SYSTEM
"file://localhost/xml-course/xml-part1/BookCatalogue.dtd">
<BookCatalogue>
    ...
</BookCatalogue>

it will be:

<?xml version="1.0"?>
<BookCatalogue xmlns="file://localhost/xml-course/xml-part1/BookCatalogue.d
cd">

where in BookCatalogue.dcd I must have:

<?xml version="1.0"?>
<DCD>
        <Description>DCD to define a Book Catalog</Description>
        <Namespace>file://localhost/xml-course/xml-part1/BookCatalog
ue.dcd</N amespace>
        <ElementDef Type="BookCatalogue" Model="Elements" Root="true">
        ...
</DCD>

(3) Will it make sense to validate a DCD?  If so, how?  Should
a DCD document reference the DCD namespace (to enable validation)
e.g.,

      <DCD xmlns="http://www.w3.org/TR/NOTE-dcd.html">
         ...
      </DCD>

(4) The examples in the DCD spec use the RDF namespace (e.g., RDF:Order)
but no where is a namespace declaration shown.  Should there be
a namespace declaration for the RDF prefix? 

i.e., 


      <DCD xmlns="http://www.w3.org/TR/NOTE-dcd.html"
           xmlns:RDF="http://www.w3.org/TR/NOTE-rdf.html">
         ...
      </DCD>
 
(5) It is not clear to me how to define an attribute whose
datatype is an enumeration and is required.  In DTD it is
specified as:

<!ATTLIST Book 
             Category (autobiography | non-fiction | fiction) #REQUIRED>

I am guessing that in DCD it is specified as:

<ElementDef Type="Book" Model="Elements">
        <AttributeDef Name="Category" Datatype="enumeration"
Occurs="Required">
                autobiography  non-fiction  fiction
        </AttributeDef>
        ...
</ElementDef>

(6) What's the difference between an ElementDef with Content="Open"
versus an ElementDef with Model="Any"?  They seem to mean the
same thing.

i.e., <ElementDef Type="foo" Model="Mixed" Content="Open"> ...

versus
      <ElementDef Type="foo" Model="Any"> ...

(7) Can somebody explain this external entity example:

<ExternalEntityDef resource="#copyrightNotice"/>

Where did this copyrightNotice thing come from?


Thanks.  /Roger


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