SYSML12 — Ambiguous Block Hierarchy

There is ambiguity in the block hierarchy shown on a bdd for parts that are nested more than one level. By illustration, assume Block A is composed of Block B which is composed of Block C. If Block A has two compositions to Block B, called b1 and b2, and Block B has two compositions to Block C, called c1 and c2, one cannot determine from the bdd whether c1 is nested within b1 or b2. The ambiguity can be removed by displaying the nesting on an ibd or by specifying the path with the dot notation. The former resovles the ambiguity in the concrete syntax only. Neither of these approaches does resolves the ambiguity on the bdd, which needs to be resolved for complex system hierarchies.

The figures above have only one (unambiguous) underlying model, but directed
relationships, such as dependencies, linked to c1 (or c2) would be ambiguous. It
would not be possible from the underlying model alone (without the notation) to tell
whether the directed relationship was referring to values of c1 properties on
instances of B that are values of the b1 property on instances of A, or values of the b2 property on instances of A, because directed relationships do not currently
support property paths, as connector ends do when NestedConnectorEnd is applied.
Introduce an abstract stereotype of DirectedRelationship with property paths for their
sources and targets, that generalizes SysML Stereotypes based on
DirectedRelationship or its specializations