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The use of object orientation and object oriented

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concepts led to what we call OOAD, object oriented

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analysis and design. OOAD is a software engineering approach

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whose main characteristics is to model a software system

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as a group of interacting objects, and we'll

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see what that means. In particular, in this lesson

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we will specifically focus on the first part of

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this, object oriented analysis, which is a requirements analysis

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technique that concentrates on modeling real world objects. And

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as I usually like to do, I would like

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to start by providing some historical perspective on object

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oriented analysis to better understand how we went from a

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function-centric world to a data-centric world. And several people

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contributed to this shift in perspective, but I'd like

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to mention a few that were particularly influential. Starting

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from James Rumbaugh, which in the 90s developed an integrated

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approach to object oriented modelling with three main aspects.

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A data aspect, so the modelling was based on

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using an extended version of entity relationship diagrams to

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describe classes and inheritance. So that's what was called

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the object model. And the second aspect has to

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do with functions. So data flow diagrams were used

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to represent the functional aspects of the system, where

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each function was then becoming a method in a class.

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So this is what is called the functional model.

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So object model and functional model. The third model

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in Rumbaugh's methodology had to do with control. So

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it was representing the dynamic aspects of a system. And

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it uses state machines, which we'll cover in more

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detail, to represent how a system would evolve going from

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one state to the other based on what happened

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to the system. These three models together represented what was

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called the Object Modeling Technique, or OMT. And

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OMT combined with contributions from several people, and in

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particular Jacobson and Booch, evolved into what we call

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the Unified Modeling Language, which is UML, which is

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probably the modeling language that most of you

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are familiar with. UML extends OMT by providing more

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diagrams and a broader view of a system from

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multiple perspectives. So, in the second part of the

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lesson, we will cover some of these

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diagrams in details, but before that, I'd like

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to talk a little bit more about object

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oriented analysis, and how we can perform it.