Hi Andy,
Hi Michael(s),
Not fully read your proposal, so can't comment on the rest ...
- Does JDO require a inheritance element for classes in an inheritance
hierarchy? If not, is there a default? The same questions apply to the
strategy attribute inside of the inheritance element.
You don't need to specify it. The default (strategy) is
* If the class has no persistence capable superclass, use "new-table"
* If the class has a persistence capable superclass, use "superclass-table"
You are right, I overlooked the default specification in chapter 15.7.
- Can I figure out whether inherited fields are mapped to the superclass
or subclass table by just looking at the inheritance strategy? I think
the answer is no, correct?
Yes you can. The inheritance always has a strategy (see default above), so you
know where the field will be persisted. I *believe* that the
<inheritance><join> is only for specifying the names of the primary key
columns in app identity cases. Perhaps there's some other use for it that I
don't know of ?
Suppose there are two non-abstract persistence-capable classes A and B.
Class B extends A. Both explicitly define the inheritance strategy
new-table. Class A maps to table TA and B maps to table TB. Then there
are still two scenarios possible, depending on where to store the
inherited fields of B instances:
(1) In table TA. Then we need a <join> element, since a class B instance
is represented by a row in table TA and a row in table TB.
(2) In table TB. No <join> element is needed since TB includes columns
for the inherited fields. So TA only has rows for class A instances, not
for B instances.
Regards Michael
--
Michael Bouschen [EMAIL PROTECTED] Engineering GmbH
mailto:[EMAIL PROTECTED] http://www.tech.spree.de/
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