A system and method for creating and modifying intelligent telephone network call processing logic trees which can be customized for individual customers and created in a user-friendly visual environment (10, 15, FIG. 3-5). Service primitives are defined as logical graph nodes (20, FIG. 2, FIG. 3) which can be visually assembled into logic trees (FIG. 5) which represent the service logic flow and which provide default values for all service options. Higher level nodes, assembled from a plurality of service primitives, can likewise be defined and stored (12, 13, 19) for later use as entities in defining yet further call processing logic trees. These call processing logic trees are interpreted to allow the service control point computers (17) to implement the services in the switched telephone network (18) by sequentially executing the specified call processing primitives. A library (12, 13, 19) of defined nodes and defined node assemblies which represent service features can thus be made available to permit graphical manipulation into complete logic trees representing new services. These logic trees are then interpreted by generic programs in the service control point to actually provide the described services.