- From: Michael Kay <mhk@mhk.me.uk>
- Date: Fri, 30 Jul 2004 10:40:52 +0100
- To: "'Jim Stanley'" <JimS@Media-Services.Com>, <xmlschema-dev@w3.org>
>
> Every time I think I've got the XML schema keys and keyrefs, they
> baffle me again.
>
I recognize the symptoms. My rule of thumb is:
if you have a rule that every E within the same Y must have a unique K,
(e.g. every "city" within the same "country" must have a unique "code") then
define the xs:key within the definition of Y, with a selector that selects E
from Y, and a field that selects K from E.
if you have a rule that every R within Y must have values of (I,J,K) that
match the values of (A,B,C) on some S within the same Y, (e.g. every
"manager" within a "division" must have the same ("first name", "last name")
as some "employee" within the same "division") then define a keyref within
the definition of Y with a selector that selects R from Y, and fields that
select I, J, and K from R.
The one that requires a clearer head than I have this morning is where the
scope of the keys is different from the scope of the keyrefs...
Michael Kay
Received on Friday, 30 July 2004 05:41:36 UTC