UML23 — Properties need not be owned

Based on UML 2.2 Diagram 9.2, it appears that Property is optionally part of StructuredClassifer. Now I understand that Properties may also be part of other things (such as associations and interfaces). But it appears that in all such places such ownership is optional.

As Properties are features, looking at the multiplicity on Feature, we see Feature:featuring Classifier is 0..*. This means that Properties (and other features) need not be part of anything.

So can you have a “free-floating” property? Where can you put it? Since Properties are not packagable, they can’t be owned by Packages.

There are (at least) two ways of solving this (I prefer the first)

1) Make properties packageable. This gives us the advantage of making a package or model-library of constants properties.

2) Fix the hole and make properties required to be owned by something.

A nearly identical argument arises from Connectors which also may be free-floating, but are not packageable.

In SysML there is some interest in making connectors packageable (possibly as we care not about code-generation in the UML sense) as it would allow us to use Binding connectors (a SysML type of connector that declares equivalence) in package or class (in SysML, Block) diagrams

Again there are two ways of solving this (I prefer the first)

1) Make connectors packageable.

2) Fix the hole and make connectors required to be owned by something.

A more general solution may be to just apply the solution strategy to features as a whole, which would minimize the changes.

The issue is incorrect to state that properties/connectors need not be owned. They both inherit Element::mustBeOwned(),
which means that they must have an owner.
Disposition: Closed - No Change