7. Computer system for model transformation reapply, comprising: a computer memory having a given programming model transformation in MDA (Model Driven Architecture); a target model generated in memory by the given transformation, the target model being a UML-type, graphical, program modeling model that generates executable code, and the target model having one or more model elements; and a processor providing a respective annotation for manually changed model elements indicating which parts are non-changeable by the given transformation and thus preservable, each annotation: (i) having an indication of extending the respective model element, and (ii) specifying extra semantics of extending the respective model element, for each annotation, the annotation specifying the extra semantics by any combination of: a string-to-string map, a containment reference collection and a non-containment reference collection; each annotation being inserted into the generated target model in a manner such that upon reapply of the given transformation, changes are made to the target model but manual changes to the model elements are preserved based on the extra semantics specified by the inserted annotations; and wherein reapplying the transformation further includes configuring the transformation with an option to detect deltas between newly generated target models and existing target model, and select which deltas to apply and which to ignore as a function of the inserted annotations.
7. Computer system for model transformation reapply, comprising: a computer memory having a given programming model transformation in MDA (Model Driven Architecture); a target model generated in memory by the given transformation, the target model being a UML-type, graphical, program modeling model that generates executable code, and the target model having one or more model elements; and a processor providing a respective annotation for manually changed model elements indicating which parts are non-changeable by the given transformation and thus preservable, each annotation: (i) having an indication of extending the respective model element, and (ii) specifying extra semantics of extending the respective model element, for each annotation, the annotation specifying the extra semantics by any combination of: a string-to-string map, a containment reference collection and a non-containment reference collection; each annotation being inserted into the generated target model in a manner such that upon reapply of the given transformation, changes are made to the target model but manual changes to the model elements are preserved based on the extra semantics specified by the inserted annotations; and wherein reapplying the transformation further includes configuring the transformation with an option to detect deltas between newly generated target models and existing target model, and select which deltas to apply and which to ignore as a function of the inserted annotations. 11. A computer system as claimed in claim 7 wherein the option further applies the chosen deltas in accordance with user interactive command given through a user interface.