[DDI-users] DDI 3.2: Schema allows double identification sequence

[Jani Hautamäki]

Quoting Jani Hautamäki:
>and, if desired, it is also possible to arrow arbitary order for the URN and ID sequence
>with the following:
>
>AbstractIdentifiableType ::= ((Agency, ID, Version)?, URN) | ((Agency, ID, Version), URN?), UserID*
>
>Feel free to test this one out. On my system both libxml2 2.7.1 and the newly
>downloaded XMLspy produced correct results.

This is obviously incorrect. What I meant was:

 AbstractIdentifiableType ::= (URN, (Agency, ID, Version)?) | ((Agency, ID, Version), URN?), UserID*

The idea being as simple as

X ::= (A, B?) | (B, A?)

This is equal to "A or B or (A and B) or (B and A)"