PARTY — The Node class issue(s)

The Node class is currently derived from CommonObject. This class is a base
class for Party and supports interfaces for parties to ask about the roles
they are involved in. There are two issues with this design. The first
issue is that these interfaces are not supported by PartyRole or
PartyRelationship. This has the effect of not allowing PartyRoles to have
Roles. As an example, an employee is a role a person plays in its
relationship with a company. A manager is role an employee plays in
relation to it's department. This would be a role of a role. To support
this, the PartyRole (and the PartyRelationship as well) should have the Node
interfaces available as well.