1. An automated method for building information technology services from a library, comprising: presenting source entities in a model layer library for user selection during development of a computer program as service modeling entities, wherein the source entities have initially predefined properties for service modeling in a markup language; prompting a user to indicate whether a first change mode or a second change mode applies; an automated computer process copying user selected ones of the source entities from the model layer library into a computer readable storage medium providing a services layer during the development of the computer program, wherein the copying generates instances in the services layer of the selected service modeling source entities, such that the services layer instances at least initially include, in a markup language, the initially predefined properties of their respective source entities; an automated computer process generating, in a binding operation, computer program code in a program layer from one or more of the instances in the services layer, wherein the binding operation includes, responsive to user selection of the first change mode, maintaining the properties of the selected ones of the source entities, including maintaining the selected source entities' properties independently of changes made in the first change mode to the properties of the service modeling entity instances in the services layer, so that the user may change the properties of the service layer service modeling instances, wherein if the change is in the first change mode, the selected source entities continue to be available in the model layer library with their respective initially predefined properties for still more user selection as service modeling entities, wherein responsive to user selection of the second change mode the automated computer process changes the selected source entities to match changed properties in the services layer of the changed service modeling entity instances; and an automated computer process generating one or more objects for runtime execution from the program layer program code.