The S1 – Service Taxonomy: Decomposition (Fit for Purpose) viewpoint of NAF v4 enables you to model ServiceSpecfications, their hierarchy (through the ServicePartOfService relationship line), and relationships of ServiceSpecifications to each other (through ServiceInterfaces and Service Connectors).

A complimentary viewpoint is the S1 Service Taxonomy diagram, where the hierarchy of ServiceSpecifications can be viewed/created as one ServiceSpecification drawn inside of another ServiceSpecification.