SYSML2 — Universal features can have many values

Clause 9.8.8.2.13 (universalClock), Description, says

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

but the Time library shows it as a package-level feature, enabling everything in the universe (instances of Anything) to identify its own universal clock (see KERML-56).

The phrase "universalClock is a single Clock" above is worded as if universalClock were a part def, rather than a part usage, giving the impression of exactly one value for universalClock across all things, but there is no constraint for this. Similarly, Clause 8.4.12.6 (Accept Action Usages) says

In particular, the Occurrences::Occurrence::localClock itself defaults to the singleton universalClock (see 9.8.8.2.13 and [KerML, 9.2.12]).

and 9.7.2.2.5 (SpatialItem) says its localClock is

A local Clock to be used as the corresponding time reference within this SpatialItem. By default this is the singleton Time::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:

    ISQSpaceTime::universalCartesianSpatial3dCoordinateFrame : CartesianSpatial3dCoordinateFrame[1] {
  /* A singleton CartesianSpatial3dCoordinateFrame that can be used as a default universal Cartesian 3D coordinate frame. */ }

This is also a top-level feature that seems intended to be "universal" in the sense above.