SYSML2_ — Variable features for SysML

Resolution KERML_-153 to issue KERML_-57 adds the concept of variable features to KerML, in order to formalize the semantics of a feature of an occurrence changing value over time. This change needs to be incorporated into SysML, since features of various kinds of occurrences in SysML (including items, parts, etc.) are presumed to have these semantics.

Incorporate variable features from KerML

In SysML models, it is already expected that features of occurrences can change over time, particularly for structural occurrences like items and parts. For example, of a Vehicle is modeled as having an engine with multiplicity 1..1, then the expectation is that any individual Vehicle as exactly one engine at any point in time, but may have different engines over time. In order to formalize these expected semantics, this resolution proposes to redefine the Feature::isVariable property from KerML in Usage to make it derived. In this way, owned features of OccurrenceDefinitions and OccurrencesUsages will, when appropriate, automatically have the expected variable feature semantics, without it having to be explicitly declared by the modeler (as it is in KerML).

Note. Resolution KERML_-153 to issue KERML_-57 has not yet been adopted by the KerML FTF. If this resolution is not adopted, then SYSML2_-510 is moot, and the changes proposed in the Revised Text of this resolution to that issue shall not be made.