SYSML2 — Some package-level features are mandatory

Package-level features do not give featuring types, and some have lower multiplicity greater than zero, meaning everything in the universe (instances of Anything), including every data value, is required to give at least that number of values to them (see KERML-56). For example, the libraries include:

Time::universalClock[1] {...} 
Observation::defaultMonitor[1] : ChangeMonitor[1] {...}
SpatialFrames::defaultFrame : SpatialFrame[1] {...}

Might be others.