Hi Lachlan,
On Jun 1, 2007, at 3:24 PM, Lachlan Deck wrote:
On 01/06/2007, at 7:32 PM, Andrus Adamchik wrote:
With this in mind we do not need an inheritance ObjRelationship,
but we may use a DbRelationship to store join semantics (anybody
mentioned that already??).
Well the original suggestion I made was for <obj-entity
superRelationship="nameOfRelationship" ...> to allow for
specifically specifying vertical inheritance (which would have the
effect of not listing this relationship along with those returned
from objEntity.getRelationships() but via
objEntity.getSuperRelationship().
This is what I was trying to avoid - introducing relationships with
special behavior.
Are you suggesting that you'd prefer <db-entity
superRelationship="nameOfRelationship" ...>
No, as DbEntities (tables) do not have inheritance among themselves.
It would be more of <obj-entity
superDbRelationship="nameOfDBRelationship" ...>, but I do believe
that this can be made implicit, as arguably there can be only one
DbRelationship between the primary keys of two tables. E.g:
SuperOE -> DB1
SubOE1 -> DB2
SubOE2 -> DB3
In this case Cayenne can easily figure out the name of DB2->DB1 and
DB3->DB1 relationships based on relationship semantics.
Another nice side effect of it is that such relationship is not a
part of the object model (ObjRelationship would've been an object
property). So there is nothing artificial about such mapping, and
no new concepts are needed in Cayenne to map it.
Can you clarify this a bit more.
See above - I don't want to redefine what ObjRelationship is. The
difference between Cayenne and EOF is that Cayenne splits DB and Java
mapping in two separate layers of metadata. EOF allows to mark a
relationship as "not included in the object model", while Cayenne
allows to map the DB relationship without mapping corresponding
ObjRelationship, essentially achieving the same thing in a different
way.
Andrus
