1. A computer-readable medium having computer-executable instructions, which when executed perform actions, comprising: receiving a definition of a new type after a version of software is created, the new type defining a property, the software, when created, supporting a first application model that includes a first set of objects, types, and methods; and adding the new type to the first application model of the software to obtain a second application model that the software supports, the second application model including a second set of objects, types, and methods including the new type.