ID/IDREF or Key/Keyref

[Ridius]

Hello.

I start to study XML and have a question. What`s the difference
between ID/IDREF
and Key/Keyref? What's better to use?

Thanks.

 

[Martin Honnen]

I start to study XML and have a question. What`s the difference
between ID/IDREF
and Key/Keyref? What's better to use?

DTDs only support ID/IDREF while XSD schemas additionally support
key/keyref. ID values need to be unique in the complete document, with
key values there is no such requirement for the complete document.
Additionally you can form a key from various element or attribute
values, that is not possible with ID. See
<http://www.w3.org/TR/xmlschema-0/#specifyingKeysAndtheirRefs>