In Section 4.1.4 we define sorts of entity in our model using expressions of the form:
where E is an entity name and each 
is a variable restricted by a
sort 
of entity on which E depends. We then take each sort of entity,
S, and for each process, P, which involves S we categorise the involvement
of S in P. The three roles which sorts of entity can have in processes
are to be originated, to be required or to be changed, which we define
using predicates of the form:
We then construct more detailed process descriptions using the expression:
and use our category information to assign appropriate instantiations of
entities (
) or their attributes to either:
and 
and 
and 
and P
changes the value of an attribute of 
.
and 
and P
removes 
.