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This model has definitely moved away from IDEF0 towards POSD. The top two levels of the model are POSD, the bottom level IDEF0. The model dispenses with much of the unnecessary detail in the top two levels of the model. The top level diagram simply recognises that the system, supply construction project, is composed from two interacting component systems, plan supplies and obtain supplies. The fact that they interact is shown by them touching in the top level diagram. They interact by means of shared component systems, orders and delivery schedule, as shown in the middle level diagrams. The middle level diagrams show the systems, plan supplies and obtain supplies, as being composed from six interacting component systems, choose suppliers, order supplies, delivery schedule, orders, deliver supplies and pay for supplies. The bottom level diagrams give compositions for five of these six components in terms of lower level components. The bottom level diagrams show how the interactions in the middle level diagrams are achieved by sharing of components - supplier list, draft orders, delivery schedule, corrections to orders, formal orders, and authorisations of payments, etc. A fuller model would show how the system, supply construction project, interacted with other systems, the customer business, the supplier businesses and the construction project. That would explain the purpose of the detailed interactions, funding, supplies, supply requirements and supplier constraints.
last revision: 21st June 1997