Multiple Root Elements in DTD

[Damodharan Ramabhadran]

This is regarding the generation of DTD's. There are certain cases when the root element of a DTD has to change since the basic XML's root element changes. The requirement is that the same DTD is needed to do the job for different XML's. Can we make the DTD accept either 'firstType' or 'secondType' as the root element(in the example shown below)? If yes, how would the DTD look like?

The XML
<?xml version="1.0" standalone="no"?>
<!DOCTYPE "firstType" SYSTEM "basic.dtd">
<firstType>
<elementA>
data
</elementA>
</firstType>
<!DOCTYPE "secondType" SYSTEM "basic.dtd">
<secondType>
<elementB>
data
</elementB>
</secondType>
Regards,
Damodharan

[Mapraputa Is]

You can use parameter entity and declare your root element as %root
basic.dtd:
<!ELEMENT %root; (elementA | elementB)+>
<!ELEMENT elementA (#PCDATA)>
<!ELEMENT elementB (#PCDATA)>
then in your XML files you can have both external subset (basic.dtd) and internal subset, in which you assign a value to %root entity:
<?xml version="1.0" standalone="no"?>
<!DOCTYPE firstType SYSTEM "basic.dtd" [
<!ENTITY % root "firstType">
]>
<firstType>
<elementA>data</elementA>
</firstType>
and
<?xml version="1.0" standalone="no"?>
<!DOCTYPE secondType SYSTEM "basic.dtd" [
<!ENTITY % root "secondType">
]>
<secondType>
<elementA>data</elementA>
</secondType>
Your real data may be different from an example you gave, so you may need to change DTD accordingly, but the basic idea should work.

[rani bedi]

good example Mapraputa.

[Damodharan Ramabhadran]

Thanks Mapraputa.