Questions on DCD

Andrew Layman andrewl at microsoft.com
Thu Jan 21 18:19:09 GMT 1999


Maneesha Jain asks how to represent the following java class in DCD:

class Kid
{
	Person mother;    *****
	Person father;
}

speculating that the answer is 

<ElementDef Type="Kid">
	<Element>Person</Element>
	<Element>Person</Element>
</ElementDef>

<ElementDef Type="Person">
 	<Element>Name</Element>
 	<Element>Address</Element>
</ElementDef>

but then saying 'What I don't understand is where in DCD can I specify that
the "Ist Person" 
information is about the "mother" and "Second Person" information is about 
"father". In concept, I was looking for a way to specify the "type" and
"name" 
for a <Element> just like in java definition marked as (*****).'

The key to the solution is to realize that of the items in the problem, two
are object types (Kid and Person) while two are relations between objects
(mother and father).   Your proposed solution doesn't quite have enought
parts, and the relation between the parts is not explicit. You can find a
proposal by me for this sort of problem at the W3c
(http://www.w3.org/TandS/QL/QL98/pp/microsoft-serializing.html).  Here is an
example of instance data reflecting a Kid and his mother and father:

  <Person id="Jane" />

  <Person id="Leroy" />

  <Kid mother="Jane" father="Leroy" />  

I'm not familiar enough with DCD to write the schema in DCD notation, so let
me write it in XML-Data notation; I'm sure you can make the translation:

  <ElementType name="Person" >
	<AttributeType name="id" dt:type="id" />     <attribute type="id" />
  <ElementType>

  <ElementType name="Kid" >
	<AttributeType name="mother" dt:type="idref" />     <attribute
type="mother" />
	<AttributeType name="father" dt:type="idref" />     <attribute
type="father" />
  <ElementType>


I hope this is helpful,

Andrew Layman

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