Package, Model, or SysML Block as UseCase owner

Again: just because a UseCase symbol appears inside the rectangle of a subject Classifier does not mean that it is owned by that Classifier and can only have that one Classifier as subject:

UML-2.5.1: 'UseCases need not be owned by their subject.'

UML-2.5.1: 'A UseCase may apply to any number of subjects. When a UseCase applies to a subject, it specifies a set of behaviors performed by that subject, which yields an observable result that is of value for Actors or other stakeholders of the subject.'

SysML (and the MagicDraw/Cameo tools) introduce some special Blocks, some of which are good candidates as UseCase owners and/or subjects:

SysML: The «system», «subsystem», «external», «domain» and «system context» keywords are for "user defined" block Stereotypes (they are not part of core SysML); they are supported in MagicDraw/Cameo as Non-Normative Extensions.

What is NOT a good idea as an owner is this beasty:

Webel: SysMLv1/UML: MagicDraw/Cameo: AVOID the the vendor-specific «useCaseModel» stereotype for Model packages, it leads to confusion with the rectangular 'subject' notation

Visit also:

SysMLv1: MagicDraw/Cameo: INTRINSIC GOTCHA: Care must be taken with ownership of Activities used as UseCase scenarios vs the ‘subject’ of the UseCase. Make sure you don’t get an Activity ‘context’ mismatch! It's up to you to manage it as intended.

Up next

GOTCHA: UML Component «subsystem» vs non-normative SysML «subsystem»

Notes

[GOTCHA, TOOL, WARNING] Webel: SysMLv1/UML: MagicDraw/Cameo: AVOID the the vendor-specific «useCaseModel» stereotype for Model packages, it leads to confusion with the rectangular 'subject' notation

[ASSERTION] Visual containment of the symbol for a UseCase in the rectangular symbol for a subject Classifier does NOT imply ownership! Packaging (ownership) of UseCases is separate from use within subjects, and a single UseCase may be used in more than one subject.

[CAPABILITY, DISPLAY, STYLE] In MagicDraw/Cameo the name and any stereotype keywords of a Classifier subject of a UseCase may be shown in the top-middle (not just top-left)

[ASSERTION, TOOL] SysML: The «system», «subsystem», «external», «domain» and «system context» keywords are for "user defined" block Stereotypes (they are not part of core SysML); they are supported in MagicDraw/Cameo as Non-Normative Extensions.

[CAPABILITY, TIP, TOOL] MagicDraw/Cameo: You can easily create your own extensions of Block to act as subjects of UseCases. The tool knows how to handle the rectangular ‘subject’ notation on Use Case Diagrams

Snippets (quotes/extracts)

[UML-2.5.1] UseCase::subject : Classifier [0..*] ... The subjects to which this UseCase applies. Each subject or its parts realize all the UseCases that apply to it.

[UML-2.5.1] A subject for a set of UseCases (sometimes called a system boundary) may be shown as a rectangle with its name in the top-left corner, with the UseCase ellipses visually located inside this rectangle.

[UML-2.5.1] A UseCase may apply to any number of subjects. When a UseCase applies to a subject, it specifies a set of behaviors performed by that subject, which yields an observable result that is of value for Actors or other stakeholders of the subject.

[UML-2.5.1] UseCases need not be owned by their subject.

[UML-2.5.1] A UseCase may be owned either by a Package or by a Classifier. Although the owning Classifier typically represents a subject to which the owned UseCases apply, this is not necessarily the case ...

[UML-2.5.1] Note that this notation for the subject classifier differs from the normal Classifier notation – it has no header or compartments.

[UML-2.5.1] Note also that the subject rectangle does not imply that the subject classifier owns the contained UseCases, but merely that the UseCases apply to that classifier.

Visit also

Visit also (backlinks)

Webel: SysMLv1: Overview of annotated Diagram Slides and Note pages related to UseCases and their combination with a System (of interest), SystemContext, and drill-down to scenario Sequence Diagrams (Interactions) and Activity Diagrams.

SysMLv1: A common misunderstanding: Just because a UseCase symbol appears inside the rectangle of a subject Classifier does NOT mean that it is owned by that Classifier and can only have that one Classifier as 'subject', and it does not imply ownership!

SysMLv1: "Should" the 'subject' of a top-level UseCase be a System or (a particular) SystemContext? Answer: Which one would you like to be correct!? [WITH EXTERNAL LINKS]

SysMLv1: MagicDraw/Cameo: Having a SystemContext as the 'subject' of each main UseCase plays nicely with the feature for automated creation of usage-level allocation swimlanes in SysML Activity Diagrams for part properties. But it's not the only way.

SysMLv1: UseCase scenario representations: On use of Activity Diagrams with swimlanes and/or Sequence Diagrams (Interactions): Actor or block-based custom «actor» on 1st (typically left) Lifeline/Swimlane, System/Subsystem on 2nd Lifeline/Swimlane

Webel: SysML for MBSE: The frequent recommendation that each UseCase have at least one "primary" scenario is a very useful and highly recommended CONVENTION (only). But it is not actually enforced by the SysML1.7 or UML2.5.1 metamodels or specifications.

Related slides (includes other tutorials)

Figure D.5 - Establishing Top Level Use Cases for the Hybrid SUV

Figure D.6 - Establishing Operational Use Cases for Drive the Vehicle

Figure D.7 - Elaborating Black Box Behavior for the “Drive the Vehicle” Use Case

Related slides (backlinks, includes other tutorials)

Useful "user-defined" stereotypes for Blocks: «system context», «system», «subsystem», «external», «domain»

Flags