Pattern-based model transformation: a metamodel-based approach to model evolution

Software systems continue to grow in complexity at a rapid pace, creating systems that are complex to build and evolve. The problems that accompany changes in requirements, system upgrades, and error correction produce a desire for software evolution methods that increase the efficiency and effectiveness of adapting complex software to changes. As software systems evolve, design models must be modified to accommodate the required changes. Techniques that control the changes to models in a systematic manner are a key to model evolution. A process that improves the ability to effectively modify a design, thereby enhancing design qualities, supports the need for improved model evolution techniques. Design patterns are common forms of reusable design experiences. They offer solutions to common design problems, reduce complexity by naming and defining abstractions, and provide a foundation for building reusable software. Well-known pattern solutions are expressed in a natural language as fragments of code which are sometimes difficult to understand and implement by software modelers. With increased focus on development of model-driven approaches, rigorous descriptions of design patterns that capture solutions during design instead of implementation are needed. This research defines an approach for the transformation of models that supports controlled model evolution. More precisely, a process for capturing design patterns in UML class diagrams is defined. This process involves defining a metamodel-level representation which specifies how a software developer can introduce design patterns into existing design models. We defined transformation patterns as an extension of the UML metamodel to characterize source and target model elements. The transformation pattern consists of specialized metamodel elements that specify the structure of source and target metamodels. Transformation patterns were specified for the Abstract Factory, Bridge and Visitor design patterns to show how the model-level transformations can be perform on patterns that represent different functionalities. We developed an action language to specify constructs which add, delete, retrieve and connect model elements. We used the constructs of the action language to define transformation specifications that implement model-level transformations on class diagrams. To determine the potential of this approach we manually implemented the transformation specification on a UML design

Formal Verification Toolkit for Requirements and Early Design Stages

Efficient flight software development from natural language requirements needs an effective way to test designs earlier in the software design cycle. A method to automatically derive logical safety constraints and the design state space from natural language requirements is described. The constraints can then be checked using a logical consistency checker and also be used in a symbolic model checker to verify the early design of the system. This method was used to verify a hybrid control design for the suit ports on NASA Johnson Space Center's Space Exploration Vehicle against safety requirements

Your memory will always be with me

Without your love and support this would not have been possible iii Acknowledgements The completion of this dissertation was only possible with the support and contributions of many people. I would like to begin by thanking my husband, Blaine, for standing behind me and for believing that I would finish this dissertation. Without his love, support and understanding, this dissertation would not be. I would like to thank my daughter Joei, for not feeling neglected when I did not have time to do those “girly ” things with her. I would also like to thank my mother, Jessie H. Judson, for instilling in me the importance of a good education and making me believe that the world was mine to conquer. Behind the scenes were my friends and family who were always there for me during my doctoral studies. I am beholden to you all for your fellowship, reassurance, and support. I would like to thank the family who gave the gift of life on February 7, 1998. Without their sacrifice and thoughtfulness, I would not have been able to enjoy the things that life has to bring nor complete this research. I thank you from the bottom of my heart. Special thanks to Dr. Doris L. Carver, my advisor, for her generous support, guidance, and patience an