1. A method for augmenting a model in a model-driven application development architecture, the method comprising: defining a task to be performed on at least one model item of a principal model, wherein said principal model is configured to facilitate automatic generation of at least one resource for use by a computer-executable application and comprises a plurality of classes, references, attributes, and associations between any of said classes; identifying at least one model item required for said task that is absent from said principal model; instantiating said absent model item in a decoration model that operates with the principal model to augment operational functionality of the principal model, where the decoration model comprises a class, a reference, and an attribute for any corresponding one of said plurality of classes, references, and attributes of the principal model; mapping said decoration model to said principal model, where the operational functionality of the principal model is augmented by the instantiated model item within the decoration model; and storing both of said models on a computer-readable medium.