TSKSESF2 — Ambiguity of the containment relationship

The Task and Session Specification defines a "contains" relationship between
a Workspace and AbstractResources contained by the workspace. An
AbstractResources may be contained within many Workspaces and Workspaces are
themselves AbstractResources. However, the semantics of "contains" with
respect to strong or weak aggregation are ambiguous. Achievement of
consistent behaviour of lifecycle operations (remove, copy and move) across
implementations requires explicit distinction between strong containment as
opposed to weak containment. Strong containment is required in order to
associate a resource with 0 to 1 principal workspace. Under strong
containment, the removal of a containing workspace implies the removal of
strongly contained resources. Under weak containment the removal of a
containing workspace implies the removal of "contained_by" relationships
held by contained resources towards the workspace. Under strong containment,
it should be illegal for a resource to strongly contain a resource it is
already strongly contained by.