UMLR — UML 2.5 Mandatory but suppressible compartments

In 11.4.4 (Classes) Notation

“A Class has four mandatory compartments: attributes, operations, receptions (see 9.2.4) and internal structure (see 11.2.4).”

However, a bit later in 11.4.5 Examples

“Figure 11.16 shows three ways of displaying the Class Window, according to the options set out for Classifier notation in 9.2.4. The top left symbol shows all compartments suppressed.”

It’s a bit confusing to have mandatory but suppressible compartments.

And in 9.2.4 (Classifier) Notation

Some compartments in Classifier shapes are mandatory and shall be supported by tools that exhibit concrete syntax conformance. Others are optional, in the sense that a conforming tool may not support such compartments.

Any compartment may be suppressed. A separator line is not drawn for a suppressed compartment. If a compartment is suppressed, no inference may be drawn about the presence or absence of elements in it.

Many readers have been confused by this use of mandatory. Apparently “mandatory” means mandatory for the tool vendor to support, but not mandatory to display.

In 11.2.4 Notation, it is clarified. E.g.,

This compartment is mandatory: all tools that conform to the concrete syntax of UML must implement it.

I’m requesting a similar clarification in 11.4.4