1. A computer-implemented method for performing operations on a computer generated model of a real-world utility network in a computer-aided design (CAD) application, the method comprising: retrieving a network part schema associated with the computer generated model, wherein the network part schema identifies a collection of network parts included in the computer generated model and wherein each network part is uniquely identified by a global identifier; parsing the network part schema to determine a first set of global identifiers associated with a set of pre-defined network part types and corresponding attributes; associating each pre-defined network part type and one or more corresponding attributes in the set of pre-defined network part types and corresponding attributes with a different pre-determined enumeration value; parsing the network part schema to determine a second set of global identifiers associated with a set of user-defined network part types and corresponding attributes; generating a different custom enumeration value for each user-defined network part type and one or more corresponding attributes in the set of user-defined network part types and corresponding attributes; associating each user-defined network part type and corresponding one or more attributes in the set of user-defined network part types and corresponding attributes with a different generated custom enumeration value; and performing an operation on at least one of the network parts in the collection of network parts included in the computer generated model based on either one of the pre-determined enumeration values or one of the custom enumeration values.