UML14 — Difference between methods, attributes and operations not clear

Summary: Normally methods, attributes and operations can be easily told from each
other:

Person.attribute
Person.method(arg1..argn) alt Person.method()
Person->Operation(arg1..argn) alt Person->Operation

There is however a situation where it is not possible to tell the
difference:

Imagine a shoe-shop with a class Shoe, and the attribute size.

you would imagine that the following

Shoe.allInstances->select(size > 10)

would give you a set of all the shoes with size bigger than 10, but it
could just as well be interpreted as the set of all shoes since an object is a set of size 1.

Considered and declined.