SYSML2_ — Definitions of View Usage are Too Restricted

View usage is restricted to have at most one definition which must be a view definition:

      /viewDefinition : ViewDefinition [0..1] {redefines partDefinition}

With this passage viewDefinition field redefines partDefinition field - this makes constraints on what partDefinition field values can be - namely (at most) one definition which must be a view definition.

This is too restrictive and precludes some valid use cases; For example, additional "instrumentation" of the view with additional properties to implement diagram properties
e.g.:

part def VendorSpecificDiagramProperties {
   attribute showGrid:Boolean;
   //other diagram style attributes here
}
//.......
view usage usersDiagram: InterconnectionView, VendorSpecificDiagramProperties {
 :>>showGrid = true;
}

This restriction could be relaxed to e.g. viewDefinition subsetting partDefinition instead of redefining, allowing more flexible use of views (just like partDefinition only subsets itemDefinition).