For accurate communication, since a project can have several participants, each from different background. Represent a given aspect of the system We will use UML, widely known and accepted UML is also well accepted in the industry

In all activities and phases Functional model: use case diagram Object model: class diagram Dynamic model: interaction diagram, activity diagram, state charts

Used during inception, requirements elicitation and requirements analysis Describe the functionality of the system Use cases focus on the behavior of the system from an external point of view. A use case describes a function provided by the system that yields a visible result for an actor

A Use Case diagram shows you some of the use cases in your system, some of the actors in your system, and the relationships between them. use case is a high−level piece of functionality that the system will provide. Use case: describes a function provided by the system that yields a result for an actor An actor is anyone or anything that interacts with the system being built.

Extend relationship: The extend-relationship connects an extension use case to a base use case. Use it for exceptional cases.

Reduce redundancy

Describe the structure of the system Conceptual class diagram Design class diagram

Play a Dice Game: A player picks up and rolls the dice. If the dice face value total seven, they win; otherwise, they lose.

Represent the dynamic behavior of the system Visualize the communication between objects

Define the dynamic behavior of an individual object as a number of states and transition between them State: particular set of values for an object

Unlike the interaction sequence diagram, which shows all the objects involved in one scenario or use case and how they collaborate together, the statechart expresses THE WHOLE LIFE OF ONE OBJECT in the domain

Three push-buttons on the lecturer’s desk: full, off, dim. Power switch on wall Always powers up ‘off’ Thereafter, press a switch to change brightness or turn on/off. Full on OffDimmed Full Dim Off Full Power on Power off Dim Off Full

Describes the behaviour of a system in terms of activities Activity = set of operations The completeness of one activity triggers a transition to another activity They are similar to flow chart

System: an organized set of communicating pats System can be decomposed into subsystems Subsystems are composed into objects

How to deal with complex systems, especially software? Model, use models to represent the system Every model focus on one area at a time Then the models will be refined

Data type: Integer, float Abstract data type: implementation independent such as set, Person Class: abstraction on o-o modelling Abstract classes: Operations (methods) Attributes Object: Messages Prototyping

Use case specification includes: Use case Name Participating actors Flow of events Entry conditions Exit conditions Quality Requirements

Use cases are written in natural languages Not technical Each use case describes all possible scenarios Scenario: instance of a use case When actors and use case communicate they exchange information