If a product definition corresponds to more than one order item there are three possibilities:
The product and order item definition (product management) does not allow picking invalid combinations, i.o.w. the set of all possible combinations is less then or equal to the configuration space for the product. A “pick list” or a decision tree is sufficient in these cases.1
The product and order item definition does allow invalid combinations because of intra-product dependencies. I.o.w the set of all possible combinations of selections and options is greater then the configuration space. A rule based system to support picking of combinations is strongly advised in this case.
There are inter-product dependencies. In this case a digital build simulation of an installation or composite product is strongly advised. This is the best approach to be able to implement and establish validation on the level of a set of devices and connections.
The configuration support requirements may be diminished by restricting the possible combinations through a concise order item definition. This is a decision that must be taken in the “definition transfer” phase, or before.2
It should be indicated on a per order item level whether validation is required or not, and when this is the case, what the scope of the validation should be, i.e. intra-product or inter-product.
1 All possible combinations from the list or “walks” through the tree define the “Configuration Space”
2 This strategy may increase the number of order items (more pre-defined combinations) , but the gains are that the selection is straightforward and does not require further checks, or better does not result in faulty deliveries.