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.

Most pages linked below are cross-referenced to many other examples throughout the site. There is also a new tutorial on the Webel recipe for pragmatic SE with SysML coming:

[STUB] TRAIL: Webel's ultimate guide to simplified yet adequate pragmatic systems engineering with functional analysis in SysMLv1 for smaller scale MBSE projects in the MagicDraw/Cameo/CATIA Magic tools

Tutorial Diagram Slide pages and tutorial sections

UseCases - UML subject vs SysML Block

Package, Model, or SysML Block as UseCase owner

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

Section: SysML-1.6 specification diagrams: 14 UseCases

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

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

Policy Note page and Webel Best Practice pages cross-linked to many examples

Webel: MBSE: SysMLv1: Prefer a custom «actor» extension of a Block (such as the non-normative External) over UML-style Actor for use as parts in IBDs and on allocation swimlanes. You can also have a Trace from a block-based «actor» to a UML-style Actor.

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!

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.

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

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]

Webel: SysMLv1: Functional analysis (isolation of white-box Activities identified via «blackbox» scenario Activities of UseCases). Recommend custom stereotype them. Candidate: «whitebox» (or a recommended SE methodology stereotype).

Webel: SysML: SE: Terminology: '«logical» handler' is used for a specific kind of «logical» subsystem (aka 'conceptual subsystem') that is a SPECIFIC collaboration of parts that handle one Activity usage in a higher level «whitebox» Activity.

HOWTO "cheat" with two-level white-boxing and tracking stereotypes because you just don't want that darn "extra" logical subsystem (conceptual subsystem) Block the systems engineers reckon you are supposed to use (and why it's easier to actually use one)

And remember always:

SysML/MBSE: Many videos, tutorial slides, and guides to MBSE with SysML present particular modelling recipes as though they are THE way to do something in SysML, not just ONE way of doing it in SysML. They are not necessarily enforced by the SysML spec.

Specific to the MagicDraw/Cameo/CATIA Magic tools

SysMLv1: MagicDraw/Cameo: Synchronising ItemFlows on Connectors with ObjectFlows in Activities using the Item Flow Manager. Nice!

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: MagicDraw/Cameo: Automated creation of usage-level allocation swimlanes in SysML Activity Diagrams for part properties of a Block. EXAMPLE: A UseCase scenario within a SystemContext as UseCase ‘subject’.

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.

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

Some important "snippet" quotes from the UML and SysMLv1 specs

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 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.'

SysML-1.6: 'The use case diagram for “Drive Vehicle” in Figure D.5 depicts the drive vehicle usage of the vehicle system. The subject (HybridSUV) and the actors (Driver, Registered Owner, Maintainer, Insurance Company, DMV) interact to realize the use case.'

Learn SysML for MBSE with the Webel IT Australia Live Online web seminar or On-Site course!

Please email or phone Webel IT Australia on +61 405 029 008 to arrange On-Site, Off-Site, or Live Online remote web training seminars and workshops.

Course: Model-Based Systems Engineering with the OMG's Systems Modeling Language® (v1) and the SysML Plugin for MagicDraw® and Cameo™ (CATIA Magic)