SPEM — a Category should not inherit from ProcessComponent.

An explicit metaclass to denote packages used for categorization.
To better reflect the semantics of packages that are used to
define a category of process elements, it could be useful to add
an explicit "Category" metaclass inheriting from Package.
Additionnally, a well-formedness rule saying "A Category can
only contain Categorizes dependencies" will help to formalize
the usage of this.
A Discipline Package obviously inherits from Category.
However a Category should not inherit from ProcessComponent.
In addition, a <<category>> stereotype could be added in
the UML profile.

Accept a minor change of wording, no extra metaclass.