Issue 18685: Forked association notation ill-formed (sysml-rtf)
Source: NIST (Dr. Conrad Bock, conrad.bock(at)nist.gov)
Nature: Revision
Severity: Significant
Summary: In Table 8.2 (Graphical paths defined by in Block Definition diagrams), rows MultibranchPart Association and MultibranchShared Association shows two association lines sharing one end (property3), implying the end is owned by two blocks (assuming the other ends are different), which isn't possible. Even if the two blocks on the opposite ends redefine property3 using the same name, the "shared" end would actually be separate elements in the model, though they would appear notationally the same.  If this is the intention, redefinition of property3 should be added to the figure, and some diagram extension text should explain that the "shared" graphical elements refer to three underlying model elements.  The notation isn't in 2.4.1 that I can find.

Resolution: Resolution: Forked association notation ill-formed

The semantics of multibranch associations are clarified in UML 2.5:

If there are two or more aggregations to the same aggregate, a conforming tool may as a purely presentational option show them as a tree by merging the aggregation ends into a single segment adorned by the solid or hollow aggregation diamond symbol. Any adornments on that single segment apply to all of the aggregation ends. The absence of an adornment on a merged segment does not imply that the properties corresponding to the suppressed adornment have equal values for all of the aggregation ends.

The notation depicted in table 8.2 in the SysML specification is misleading.
Revised Text: The following changes in table 8.2 must be made:


*Rename "MultibranchPart Association" to "MultibranchPart Associations"
*Rename "MultibranchShared Association" to "MultibranchShared Associations"
*In row "MultibranchPart Association" add label "association2" to the lower association.
*In row "MultibranchShared Association" add label "association2" to the lower association.
Actions taken:
April 24, 2013: received issue
January 3, 2017: Resolved
April 6, 2017: closed issue
Discussion: 

End of Annotations:=====

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        Date: 24 Apr 2013 09:11:46 -0400
        To: <issues@omg.org>
        Subject: Issue/Bug Report
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        *******************************************************************************
        Name:            Conrad Bock
        Employer:        NIST
        mailFrom:        conrad.bock@nist.gov
        Terms_Agreement: I agree
        Specification:   SysML 1.3
        Section:         Classes
        FormalNumber:    ptc/2011-08-10
        Version:         1.3
        Doc_Year:        2012
        Doc_Month:       June
        Doc_Day:         01
        Page:
        Title:           Forked association notation ill-formed
        Nature:          Revision
        Severity:        Significant
        CODE:            3TMw8
        B1:              Report Issue

        Description:  In Table 8.2 (Graphical paths defined by in Block Definition diagrams), rows MultibranchPart Association and MultibranchShared Association shows two association lines sharing one end (property3), implying the end is owned by two blocks (assuming the other ends are different), which isn't possible. Even if the two blocks on the opposite ends redefine property3 using the same name, the "shared" end would actually be separate elements in the model, though they would appear notationally the same.  If this is the intention, redefinition of property3 should be added to the figure, and some diagram extension text should explain that the "shared" graphical elements refer to three underlying model elements.  The notation isn't in 2.4.1 that I can find.