ISSUE 119: Projection and Keys

["Barack, Ron" <ron.barack@sap.com>]

Title: ISSUE 119: Projection and Keys

Hi Everyone,

Here is a link to the email that contains my last proposal:  http://www.oasis-open.org/apps/org/workgroup/sdo/email/archives/200808/msg00060.html

I'll repeat the section relevant to identity when projecting from keys to entities:

Conversely, when projecting from a key to an entity then for each distinct key value within the graph being projected, all references to that key must resolve to the same entity.

In many scenarios data will round-trip between contexts, including between contexts in which entity map to keys. Let us consider two context Ce and Ck, representing the entity and the key context, respectively, and a DataObject Oe, in context Ce. Projecting Oe into Ck returns a DataObject, Ok. The transitive closure reachable from Ok is Gk. Every key value in Gk maps to an single entity in Ce, and it is this entity is that is found when Ok (and effective, all of Gk) is projected back into Ce. In cases where the user has set a key property to a value that is not found in Gk, then, as a result of projecting Ok into Ce, a new entity will be created. The created entity has default values for all properties other than the key fields.

Ron