IDREF

[Marcus Carr]

Rick Jelliffe wrote:

> Many people recommend that an attribute should only be called
> "ID" if it is an ID attribute. So in the following, x1 is good and
> x2 is naughty:
>
> <!ATTLIST x1           ID     ID            #REQURIED>
> <!ATTLIST x2           ID     CDATA  #REQURIED>
>
> I think it is good practice anyway: dont name an attribute
> using an XML keyword if that is not the type you want.

True, but the requirements of the attribute may not be known until processing
time. You may use a parameter entity in the declaration subset and assign the
value based on whether the parser will have access to the rest of the dataset or
whether this is a subset that would result on the generation of useless and
unwanted errors, ie:

<!ATTLIST x1           ID     %IDorCDATA;         #REQURIED>

in the DTD, and then, depending on the doctype element, generate either:

<!DOCTYPE WholeDataSet  PUBLIC   "-//My//DTD for example//EN"  [
<!ATTLIST IDorCDATA        "ID">]>

or:

<!DOCTYPE DataSetFrag  PUBLIC   "-//My//DTD for example//EN"  [
<!ATTLIST IDorCDATA        "CDATA">]>

at the head of the instance.


--
Regards

Marcus Carr                  email:  mrc at allette.com.au
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