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Note for Web Technologies - WT By Ashutosh Jaiswal

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www.jntuworld.com Introducing the UML (Unified Modeling Language) As the world becomes more complex, the computer-based systems that inhabit the world also must increase in complexity. They often involve multiple pieces of hardware and software, networked across great distances, linked to databases that contain mountains of information. If you want to make systems that deal with this, how do you get your hands around the complexity? The key is to organize the design process in a way that clients, analysts, programmers and other involved in system development can understand and agree on. The UML provides the organization. Consider this: Would you tell a building contractor that you want a 4 bedroom, 3 bath home, about 2000 square feet - Start building it! We'll hammer out the details as we go along? We all know this is ludicrous. But sadly, this method of development is all too common in the software industry. Just as you would work with an architect to design a blueprint that would diagram exactly how the house is to be built, you will work with us on an UML diagram that will document exactly how your custom software system will be built. What is UML? The Unified Modeling Language (UML) is a standard language for specifying, visualizing, constructing, and documenting the artifacts of software systems, as well as for business modeling and other non-software systems. The UML represents a collection of best engineering practices that have proven successful in the modeling of large and complex systems. The UML is a very important part of developing object oriented software and the software development process. The UML uses mostly graphical notations to express the design of software projects. Using the UML helps project teams communicate, explore potential designs, and validate the architectural design of the software. The UML was released in 1997 as a method to diagram software design. It was designed by a consortium of the best minds in object oriented analysis and design. It is by far the most exciting thing to happen to the software industry in recent years. Every other engineering discipline has a standard method of documentation. Electronic engineers have schematic diagrams, architects and mechanical engineers have blueprints and mechanical diagrams. The software industry now has UML. Goals of UML The primary goals in the design of the UML were: 1. Provide users with a ready-to-use, expressive visual modeling language so they can develop and exchange meaningful models. 2. Provide extensibility and specialization mechanisms to extend the core concepts. 3. Be independent of particular programming languages and development processes. CSE Department, VNRVJIET 1 www.jntuworld.com

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www.jntuworld.com 4. Provide a formal basis for understanding the modeling language. 5. Encourage the growth of the OO tools market. 6. Support higher-level development concepts such as collaborations, frameworks, patterns and components. 7. Integrate best practices. Before we move on next lesson consider some of the benefits of UML: 1 Your software system is professionally designed and documented before it is coded. You will know exactly what you are getting, in advance. 2 Since system design comes first, reusable code is easily spotted and coded with the highest efficiency. You will have lower development costs. 3 Logic 'holes' can be spotted in the design drawings. Your software will behave as you expect it to. There are fewer surprises. 4 The overall system design will dictate the way the software is developed. The right decisions are made before you are married to poorly written code. Again, your overall costs will be less. 5 UML lets us see the big picture. We can develop more memory and processor efficient systems. 6 When we come back to make modifications to your system, it is much easier to work on a system that has UML documentation. Much less 'relearning' takes place. Your system maintenance costs will be lower. 7 If you should find the need to work with another developer, the UML diagrams will allow them to get up to speed quickly in your custom system. Think of it as a schematic to a radio. How could a tech fix it without it? 8 If we need to communicate with outside contractors or even your own programmers, it is much more efficient. Using the Unified Modeling Language will result in lower overall costs, more reliable and efficient software, and a better relationship with all parties involved. Software documented with UML can be modified much more efficiently. Your software will have a future. Modeling of systems, old way vs. new way During this course we will deal with systems, or parts of some larger systems. System is a combination of software and hardware that provides a solution for a business problem. Process of developing that system involves a lot of people. First of all is the client, the person who has the problem to be solved. An analyst documents the client's problem and relays it to developers, CSE Department, VNRVJIET 2 www.jntuworld.com

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www.jntuworld.com programmers who build the software that solves the problem, test it and deploy it on computer hardware. This is necessary because systems today are so complex, knowledge has become so specialized that one person can't know all the facets of a business, understand the problem, design a solution, translate it into a program, deploy the program onto hardware, and make sure the hardware components all work together correctly. The waterfall method for modeling of systems The old way of system modeling, known as the waterfall method, specifies that analysis, design, coding and deployment follow one another. Only when one is complete can the next one begin. If an analyst hands off analysis to a designer, who hands off a design to a developer, chances are that the three team members will rarely work together and share important insights. Usually the adherents of the waterfall method give coding a big amount of project time; it takes a valuable time away from analysis and design. In the new way, contemporary software engineering stress continuing interplay among the stages of development. Analysts and designers, for example, go back and forth to evolve a solid foundation for the programmers. Programmers, in turn, interact with analysts and designers to share their insights, modify designs, and strengthen their code. The advantage is that as understanding grows, the team incorporates new ideas and builds a stronger system. CSE Department, VNRVJIET 3 www.jntuworld.com

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www.jntuworld.com UML Diagram Set of Symbols This is the complete set of symbols that UML introduces in its diagrams. Structural Elements Class: Classes are composed of three things: a name, attributes, and operations. Below is an example of a class. Interface: The symbol of interface is Use case: A use case is a set of scenarios that describing an interaction between a user and a system. The following is the symbol for use case. Node: The symbol for the node is as shown below. Component: The symbol for the component is as shown below. CSE Department, VNRVJIET 4 www.jntuworld.com

Lecture Notes