Systems Modeling Language (SysML) 2.0 FTF — Open Issues - OMG Issue Tracker

Key: SYSML2-84

Status: closed

Source: Model Driven Solutions ( Mr. Ed Seidewitz)

Summary:

The second line of the following does not parse:

abstract connection c1;
abstract connection c2 = c3; // Error: No viable alternative at input '='

The reason for this is that the ConnectionUsage production uses UsageDeclaration (see subclause 8.2.2.13.1):

ConnectionUsage =
    OccurrenceUsagePrefix
    ( 'connection' UsageDeclaration
      ( 'connect' ConnectorPart )?
    | 'connect' ConnectorPart )
    UsageBody

However, UsageDeclaration does not include ValuePart, which provides the syntax for feature values (see 8.2.2.6.2):

Usage =
    UsageDeclaration UsageCompletion
UsageDeclaration : Usage =
    Identification FeatureSpecializationPart?
UsageCompletion : Usage =
    ValuePart? UsageBody

On the other hand, 7.13.2 states that “A connection definition or usage (that is not of a more specialized kind) is declared as a kind of occurrence definition or usage (see 7.9.2), using the kind keyword connection”, and an occurrence declaration (in the informal sense) can, in general, include a feature value, so it would be expected to be allowable for a connection, too.

Note that this is also a problem for interactions, but not for messages or flow connections, which explicitly allow a ValuePart (see 8.2.2.13.4):

MessageDeclaration : FlowConnectionUsage =
      UsageDeclaration ValuePart?
      ( 'of' ownedRelationship += ItemFeatureMember )?
      ( 'from' ownedRelationship += MessageEventMember
        'to' ownedRelationship += MessageEventMember
      )?
    | ownedRelationship += MessageEventMember 'to'
      ownedRelationship += MessageEventMember

FlowConnectionDeclaration : FlowConnectionUsage =
      UsageDeclaration ValuePart?
      ( 'of'  ownedRelationship += FlowPayloadFeatureMember )?
      ( 'from' ownedRelationship += FlowEndMember
        'to'   ownedRelationship += FlowEndMember )?
    | ownedRelationship += FlowEndMember 'to'
      ownedRelationship += FlowEndMember

Reported: SysML 2.0a1 — Thu, 27 Apr 2023 21:30 GMT

Disposition: Resolved — SysML 2.0b2

Disposition Summary:

Correct textual notation for ConnectionUsage and InteractionUsage

Not including ValuePart in these productions is clearly undesirable. The productions are straightforwardly updated to add it in as it is included in the notation for other kinds of usages.

Updated: Tue, 1 Jul 2025 14:47 GMT