SYSML — SysML:Usiing a BDD for Activities

The SysML spec says that a BDD can be used for functional decomposition because an Activity is a Class in UML. (see the end of 11.1; 11.3.1.1)

However, the spec says elsewhere that a BDD can only be for Blocks, Packages, or constraint blocks.

For example, Annex A.1 (p 167)

The following are the designated model elements

associated with the different diagram kinds.

• activity diagram - activity

• block definition diagram - block, package, or constraint block

• internal block diagram - block or constraint block

From 8.3.2, it is clear that while a block is a class, a class is not a block.

From this, it is unclear how a block diagram can really (formally) be for an activity.

Possible solutions

1) Let a bdd for any classifier

This has the extra advantage of allowing bdd’s for actors, ports, etc.

2) Change the annex to allow a bdd to be for activities (and perhaps actors, ports…)

3) Change the definition of a SysML activity to be both a UML4SysML Activity and a SysML Block (probably too complicated)

Also the example diagrams (such as figure 11.1 and the figure in Table 11.3 row 1) should have a complete diagram header. This should at least include the model element type for the diagram (to be consistent with the solution above).

They should also have a «diagramUsage» if one is required (as implied by Table 11.3)

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