UPDM — ActivityRealization

it is difficult to interpret the purpose of this from the definition (which
is somewhat Byzantine), but this seems in essence to be a relationship between an Op
Activity and a System Function to show that the System Function realises the Op Activity. If
this is the case, it seems strange that UPDM has not used the usual UML approach of a
dependency. Alternatively, it could be argued that as these are classes (i.e. types of activity),
then the system function is a special way of conducting an operational activity, so a
Generalisation relationship might be acceptable. The use of an Association seems very
unusual.