There are several special types of lookups in the system which have different requirements or return a different object than the standard lookups.
The Category lookup (http://restapi.lucity.net/gbaMS/Work/WorkOrders.svc/CategoryCode/ or http://restapi.lucity.net/gbaMS/Work/Requests.svc/CategoryCode/) includes information required to re-construct a tree for the category.
Other lookups in the system will depend upon the current state of an object and therefore require a POST request instead of a GET request and requre that the current object be provided in the body of the request. These are commonly referred to as Value Lookups. For example, in the water pipes module, the values for the FromNode depend upon the value of the FromNodeType. If the FromNodeType is a valve, the FromNode lookup will return a list of valves. If the FromNodeType is a hydrant, the list will be hydrants, and so on.