Containment management
As it was previously described, PAMELA metamodel supports containment.
Entities containment is modeled through the use of @Embedded annotation, defined on a ModelProperty. Underlying semantics states that an instance of a ModelEntity is embedded in a container ModelEntity if this instance is present in collection denoted by related ModelProperty applied to container instance. Resulting containment relationships are internally represented as a directed acyclic graph.
Those relationships are used to support miscellaneous features, such as modified status for any of instances involved in an object graph, as well as closure computation, cloning and clipboard operations.
Containment closure computation
In graph theory and combinatorial optimization, a closure of a directed graph is a set of vertices with no outgoing edges. That is, the graph should have no edges that start within the closure and end outside the closure. PAMELA frameworks relies on a internal scheme which computes the closure of an input graph infered from a explicit set of objects, considered as vertices, and following containment relationships, considered as edges. This containment closure computation is especially used in cloning support.
modified status support
Following figure presents life-cycle for any object managed with PAMELA. Any call to a write-access ModelProperty (properties using set:, add:, add:AtIndex:, remove:, delete: and undelete: protocols) implies modified status for related object to be set to true.
In the context of containment relationships, this status is propagated along container hierarchy: any object beeing modified implies its container (which may be an unique object or a set of objects) being modified too. modified status for a given instance may be retrieved using isModified() method defined in AccessibleProxyObject Java interface. In the case of a custom method beeing implemented, which has side-effect (impacting its internal data), a setModified(boolean) method is offered to the developper to indicates the modification. Saving object graph brings back object status in Alive/Saved status: in this case isModified() method returns false.
