SysML 1.7 RTF Avatar
  1. OMG Issue

SYSML17 — About Block constraint "3" removed by SysML v1.6

  • Key: SYSML17-227
  • Status: open  
  • Source: Airbus Group ( Yves Bernard)
  • Summary:

    Ed Seidewitz caught this:
    While researching a question forwarded to me by Sandy, I noticed what seems to be an inconsistency in the SysML 1.6 specification. SysML 1.5 included the following constraint under the Block stereotype:

    [3] In the UML metamodel on which SysML is built, any instance of the Property metaclass that is typed by a block (a Class with the «block» stereotype applied) and which is owned by an Association must [sic] not have a name and may not be defined as a navigable owned end of the association. (While the Property has a “name” property as defined by its NamedElement superclass, the value of the “name” property, which is optional, must be missing.)

    However, this constraint has been removed from the SysML 1.6 spec (and it is not included in the XMI).

    Issue SYSML16-310, which was merged into the resolution of SYSML16-274, addresses this constraint. In the comments on 310, Yves made a suggestion to remove the constraint, but then added a subsequent comment that reads: “Discussed during RTF weekly meeting on Sep 21: Ok for deleting the fits part of the sentence: "In the UML metamodel on which SysML is built" but any other change requires a separate issue” (SYSM16-310 - comment-17892, 21/Sep/17). There is also an earlier comment on the resolution to SYSML16-295 that notes “We had a discussion about constraint[3]. It seems the be not correct. Yves or Conrad will file an issue about that.” (SYSML16-295/SYSML16-297 - comment-17815, 31/Aug/17])

    But I cannot find any separate issue that was actually filed to remove constraint 3. The constraint was simply not included in the revised text in the resolution of SYSML16-274, and hence ended up being left out of the SysML 1.7 beta spec.

    So, there does not seem to be an apparent intent of the RTF to remove this constraint in SysML 1.6. Indeed, the following paragraph remains in the description section of subclause 8.3.2.3 Block in the 1.6 spec:

    “SysML excludes variations of associations in UML in which navigable ends can be owned directly by the association. In SysML, navigation is equivalent to a named property owned directly by a block. The only form of an association end that SysML allows an association to own directly is an unnamed end used to carry an inverse multiplicity of a reference property. This unnamed end provides a metamodel element to record an inverse multiplicity, to cover the specific case of a unidirectional reference that defines no named property for navigation in the inverse direction. SysML enforces its equivalence of navigation and ownership by means of constraints that the block stereotype enforces on the existing UML metamodel.”

    This is text certainly no longer true without constraint 3, and I would have expected it to have been removed or updated if there had actually been an affirmative resolution to remove the constraint.

  • Reported: SysML 1.6 — Thu, 11 Apr 2019 13:24 GMT
  • Updated: Thu, 11 Apr 2019 13:35 GMT