Troy Cauble wrote:
> In comp.text.xml Charles Packer <mailbox@c...> wrote:
>> Does XML have a way to refer to duplicated data?
> 
>> .
>> .
>> <situation> something </situation>
>> <action1> action specific to something </action1>
>> <action2>
>>        .
>>        . ...often done in any situation...
>>        .
>> </action2>
>> <situation) something else </situation>
>> <action1> action specific to something else</action1>
>> ???
>> .
>> .
>> .
>>
>> ...the question marks are where I want to insert
>> correct XML that compactly signals a second use of
>> datum "action2". I learned from an XML tutorial that I can
>> assign an _attribute_ to action2. Might a solution to
>> the problem involve an attribute? The tutorials I perused
>> didn't have anything about this use of attributes.
> 
> 
> You could have optional id and ref elements.
> 
> 	<action id='myUniqueId'>blah....</action>
> 	...
> 	<action ref='myUniqueId'/>
> 
> with documentation saying to use a ref attribute *OR* content.
> Better than documentation is something you can validate
> with DTD/XML Schema/whatever.  Such as 
> 
> 	<actionref ref='myUniqueId'/>
> 
> Where actionref requires ref, does not allow content, and can be
> used wherever action can.
> 
> Depending on your app, you might consider it poor form to
> reference an action in a situation from another situation.
> So you might want a section of
> 
> 	<actiondefs>
> 		<actiondef id='myUniqueId'>blah...</actiondef>
> 	</actiondefs>
> 
> where id is required (and no longer allowed in action).
> 
> Also, you probably don't want to number your action element
> names "action1", "action2", etc.  Just use "action".  Order
> is significant within sub-elements.

Sadly, SGML's CONREF (Content Reference) attribute type, which was 
(among other things) for this exact type of situation, never made it 
into XML.

///Peter