? ??Module 2 Principles of Visual ModelingTopicsObjectivesWhere Are We?What Is a Model?Why Model?The Importance of ModelingSoftware Teams Often Do Not ModelModel Driven Architecture (MDA)MDA ViewpointsWhere Are We?Four Principles of ModelingPrinciple 1: The Choice of Model is ImportantPrinciple 2: Levels of Precision May DifferPrinciple 3: The Best Models Are Connected to RealityPrinciple 4: No Single Model Is SufficientWhere Are We?What Is the UML?The UML Is a Language for VisualizingThe UML Is a Language for SpecifyingThe UML Is a Language for ConstructingThe UML Is a Language for DocumentingHistory of the UMLInputs to the UMLWhere Are We?A Language Is Not Enough to Build a SystemWhat Type of Process Most Benefits the UML?A Use-Case Driven ProcessAn Architecture-Centric ProcessAn Iterative and Incremental ProcessIterative DevelopmentReview► ► ► Module 2 Principles of Visual Modeling 1IBM Software Group®Essentials of Visual Modeling with UML 2.0Module 2: Principles of Visual Modeling Topics What Is a Model? ................................................................................................. 2-4 Four Principles of Modeling................................................................................ 2-11 What Is the UML? .............................................................................................. 2-17 A Language Is Not Enough to Build a System....................................................... 2-25 © Copyright IBM Corp. 2004 2 - 1 Course materials may not be reproduced in whole or in part without the prior written permission of IBM.Essentials of Visual Modeling with UML 2.0 Objectives 2Objectives Describe the importance of visual modeling and the role of Model Driven Architecture. Define the four principles of visual modeling. Explain what the Unified Modeling Language (UML) represents. Define the type of process that best relates to the UML. 2 - 2 © Copyright IBM Corp. 2004 Course materials may not be reproduced in whole or in part without the prior written permission of IBM.Module 2 - Principles of Visual Modeling Where Are We? 3Where Are We? What is modeling? Four principles of visual modeling The UML Process and visual modeling © Copyright IBM Corp. 2004 2 - 3 Course materials may not be reproduced in whole or in part without the prior written permission of IBM.Essentials of Visual Modeling with UML 2.0 What Is a Model? 4What Is a Model? A model is a simplification of reality. According to Grady Booch, IBM Fellow, a model provides the blueprints of a system. Models may encompass detailed plans, as well as more general plans that give a 30,000-foot view of the system under construction. A good model includes those elements that are not relevant to the given level of abstraction. Every system may be described from different aspects using different models, and each model is therefore a semantically closed abstraction of the system. A model may be structural, emphasizing the organization of the system, or it may be behavioral, emphasizing the dynamics of the system. 2 - 4 © Copyright IBM Corp. 2004 Course materials may not be reproduced in whole or in part without the prior written permission of IBM.Module 2 - Principles of Visual Modeling Why Model? 5Why Model? Modeling achieves four aims: Helps you to visualize a system as you want it to be. Permits you to specify the structure or behavior of a system. Gives you a template that guides you in constructing a system. Documents the decisions you have made. You build models of complex systems because you cannot comprehend such a system in its entirety. You build models to better understand the system you are developing. According to Booch in The Unified Modeling Language User Guide, modeling achieves four aims: 1. Models help you to visualize a system, as you want it to be. A model helps the software team communicate the vision for the system being developed. It is difficult for a software team to have a unified vision of a system that is described only in specification and requirement documents. Models bring about understanding of the system. 2. Models permit you to specify the structure of behavior of a system. A model allows how to document system behavior and structure before coding the system. 3. Models give a template that guide you in constructing a system. A model is an invaluable tool during construction. It serves as a road map for a developer. Have you experienced a situation where a developer coded incorrect behavior because he or she was confused over the wording in a requirements document? Modeling helps alleviate that situation. 4. Models document the decisions you’ve made. Models are valuable tools in the long term because they give “hard” information on design decisions. You don’t need to rely on someone’s memory. © Copyright IBM Corp. 2004 2 - 5 Course materials may not be reproduced in whole or in part without the prior written permission of IBM.Essentials of Visual Modeling with UML 2.0 The Importance of Modeling 6The Importance of ModelingPaper Airplane Fighter JetLess Important More Important You can take a piece of paper and a paper clip, and, in a few minutes, have a paper airplane that entertains your kids. If it isn’t built just right, you can always start over and build another airplane. Would it be smart for you to build a fighter jet in the same way? That is, start with some steel, nuts, bolts, and wiring and go right to work. Of course not. You’re building an airplane that costs millions of dollars, and the cost of failure is high. You’re also be part of a much larger team, needing blueprints and models to effectively communicate with one another. (The Unified Modeling Language User Guide, Booch, 1999.) 2 - 6 © Copyright IBM Corp. 2004 Course materials may not be reproduced in whole or in part without the prior written permission of IBM.Module 2 - Principles of Visual Modeling Software Teams Often Do Not Model 7Software Teams Often Do Not Model Many software teams build applications approaching the problem like they were building paper airplanes Start coding from project requirements Work longer hours and create more code Lacks any planned architecture Doomed to failure Modeling is a common thread to successful projects If defense contractors want to build fighter jets for the government, they need to