At first archetypes can be a little overwhelming. With time a large community has taken interest and now has a shared view of what an archetype is. The next step taken was to create templates. This allowed aggregation of archetypes into one larger constraint statement and included some differential statements about, for example, not using some parts of an archetype or making a maximum value a little smaller in a particular context.
So templates are composite constraint statements that include some differential statements. Now we have the idea of constraints, differentials and composites. Do these apply in any other way to archetypes?
As people began to create specialised archetypes it became clear that these were difficult to maintain. Any changes in the parent archetype meant that the child had to be updated; a difficult maintenance problem (ask the CfH program in the UK). Thomas Beale has extended the idea of a differential constraint to be a stand alone statement on specialisation. This enables the specialised archetype (as a normal constraint statement) to be generated from the differential constraint and the parent archetype.
Differential constraints are therefore used in specialisation and in templates. What can we say about differential statements?
- A differential constraint as a stand alone statement is a specialisation.
- A stand alone differential constraint combined with a constraint -> a constraint.
- A differential constraint as part of a constraint statement is a composite constraint or template.