UML25 — Section 11: feature inheritance should be orthogonal to the topology of well-formed connections in a structured classifi

Title: UML2.5, section 11: feature inheritance (of attribute properties,
ports and connectors) should be orthogonal to the topology of well-formed
connections in a structured classifier

Summary:

SysML uses extensively UML's StructuredClassifiers.
In UML 2.4.1, the well-formedness constraints for UML's
StructuredClassifiers were written in English only.
In UML 2.5, the well-formedness constraints have both English descriptions
and OCL specifications.

Unfortunately, the UML 2.5 OCL specifications for the well-formedness of
UML's StructuredClassifiers are too restrictive for SysML in 3 areas:

1) StructuredClassifier::/role is a derived union that is subsetted only
once by StructuredClassifier::ownedAttribute.

This means that inherited attributes of a StructuredClassifier are not
considered to be roles of that StructuredClassifier.

2) StructuredClassifier::/part is derived and the derivation is:
ownedAttribute->select(isComposite)

This means that inherited attributes of a StructuredClassifier are not
considered to be parts of that StructuredClassifier.

3) Connector has a constraint, roles, stated as follows:

The ConnectableElements attached as roles to each ConnectorEnd owned by a
Connector must be roles of the Classifier that owned the Connector, or
they must be Ports of such roles.

inv: structuredClassifier <> null
and
end->forAll( e |
structuredClassifier.role->includes(e.role)
or
e.role.oclIsKindOf(Port) and
structuredClassifier.role->includes(e.partWithPort))

There is a significant conceptual asymmetry between the two disjuncts of
the forAll() clause.

The first disjunct is: structuredClassifier.role->includes(e.role)

This restricts the ConnectableElement to be a role of the
StructuredClassifier owning the Connector; that is, the ConnectableElement
must be an ownedAttribute of that StructuredClassifier.

The second disjunct is: e.role.oclIsKindOf(Port) and
structuredClassifier.role->includes(e.partWithPort)

This also restricts the ConnectableElement::partWithPort to be a role of
the StructuredClassifier owning the Connector; however, the
ConnectableElement Port may be inherited!
(see ConnectorEnd::role_and_part_with_port)

The conceptual asymmetry is that it is OK to connect inherited ports of
owned attributes but it is not OK to connect inherited attributes.

>From a conceptual point of view, UML 2.5 does not provide a rationale for
restricting the connectivity of UML StructuredClassifiers to owned
attributes only.
>From a conceptual point of view, feature inheritance (I.e., of attribute
properties and of connectors) should be orthogonal to the topology of
connections in a StructuredClassifier.

Merged with 18697