KerML 1.0b2 FTF Avatar
  1. OMG Issue

KERML — Universal features can have many values

  • Key: KERML-56
  • Status: open  
  • Source: NIST ( Mr. Conrad Bock)
  • Summary:

    [From Vince Molnar] Clause 9.2.12.2.7 (universalClock), Description, says

    universalClock is a single Clock that can be used as a default universal time reference.

    but the Clocks library shows it as a package-level feature, ie, it has no featuring type, which Clauses 7.3.4.1 Features (Overview) and 8.3.3.3.3 (Feature) explain as

    The domain of features with no explicit featuring types is the type Anything from the Base library model (see 9.2.2).

    The domain of a Feature with no featuringTyps is implicitly the most general Type Base::Anything from the Kernel Semantic Library.

    enabling everything in the universe (instances of Anything) to identify its own universal clock.

    The phrase "universalClock is a single Clock" above is worded as if universalClock were a class, rather than a feature, giving the impression of exactly one value for universalClock across all things, but there is no constraint for this. Similarly, library documentation for Occurrence::localClock says:

    By default this is the singleton universalClock.

    The term "singleton" usually refers to instances of a class, rather than values of a feature, giving the impression of exactly one value for universalClock across all things.

    Might be other features like this. For example, from the library:

    Observation::defaultMonitor[1] : ChangeMonitor {doc
      /* defaultMonitor is a single ChangeMonitor that can be used as a default. * }
    
    SpatialFrames::defaultFrame : SpatialFrame[1] { doc
      /* defaultFrame is a fixed SpatialFrame used as a universal default. */ }
    

    These are also top-level features that seem intended to be "universal" in the sense above.

  • Reported: KerML 1.0a1 — Mon, 1 May 2023 13:52 GMT
  • Updated: Mon, 8 Apr 2024 21:42 GMT