Use of ID/IDREF
ID/IDREF is a mechanism which can be used to remove duplication of data in XML instances. This has been discussed for 6+ years. Should the XML ITS allow for the use of the id/idref pattern in the XML? (use of id to act as a reference to another content part of the message elsewhere) This is perceived as an ITS feature since it is supported by other technologies such as CORBA. However though this is a recognized pattern of use in XML, it is not standard or widely used. The pattern imposes on onus of the implementer to track the id and resolve the references. This is very difficult for xpaths. So the XML ITS recommends that id/idref cannot be used in the message. MnM asked INM to consider allowing this use.
The ID/IDREF mecahnism can be used by the ITS to minimize the size of messages on the wire. Whenever one encounters an IDREF one would have to process the thing being referenced. It is a potential ITS level feature. It turned out that this is not very robust, and hasn't been used substantially. Horrible for transforms. Stylesheets are basically impossible.
The XML SIG has studied the use of XML ID/IDREF. Based on the outcome of that they will move the motion during the upcoming WGM that ID/IDREF can't be used within the ITS (because of technical implementation reasons as will be stated above).
Q: (Joseph Waller) Is ID/IDRef model derived or not? and if so (or not) how does this end up in schema? A: The concept doesn't exist within the RIM.