UMLR — DI refers to putting the Diagram Kind in bold...

The DI material for UML 2.5 on p 686 Appendix B
"The diagram kind in the heading shall be rendered in boldface"

Unfortunately, there is no field anywhere defined to be Diagram kind or Diagramkind, anywhere in UML 2.5 or the DI annex.

Apparently, what was meant was the kind field in annex A, p 681.

[<kind>]<name>[<parameters>]
The heading of a diagram represents the kind, name, and parameters of the namespace enclosing or the model element owning elements that are represented by symbols in the contents area.

The DI material also refers to diagram kind on p 696 in the context of activity diagrams vs activity frames.

I suggest that frameKind be formally defined and referred to properly.