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Information Technology
ITEC 3010
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Systems Analysis and Design I ITEC3010 – Fall 2010 – Luiz Cysneiros Lecture 7 – Object-Oriented Approach to Requirements – Nov 2 The Unified Modeling Language and the Object Management Group - Object-oriented modeling notation is Unified Modeling Language (UML) - UML was presented to Object Management Group (OMG) as standard modeling technique - Purpose of Object Management Group o Promote theory and practice of object technology for development of distributed systems o Provide common architectural framework for OO Object-Oriented Requirements - Object-oriented system requirements are specified and documented through process of building models - Systems development process starts with identification of events and things - Events are business processes that new system must address - Things are problem domain objects involved in business process Object-Oriented Approach Models - Class diagram – definition of system components - Use case diagrams and use case descriptions – What are user roles and how they use the system - Systems sequence diagrams (SSDs) – define inputs and outputs and sequence of interactions between user and system for a use case - State chart diagrams – describe states of each object - Activity diagrams – describe user activities Overview - The objective of requirements definition is understanding – understanding the users’ needs, the business processes, and the systems to support business processes - Understand and define requirements for a new system using object-oriented analysis models and techniques - Line between object-oriented analysis and object-oriented design is somewhat fuzzy o Iterative approach to development o Models built in analysis are refined during design The Class Diagram - There are two kinds of descriptions of systems o Structural information (components of the system) o Behavioral information (logic performed by components) - Class diagram provides definition of structural components of the system - The other OO diagrams (e.g. use case, sequence, collaboration) focus on activities the system performs - NOTE – with OO Analysis, the class diagrams describes system requirements that can map very closely to the structure (i.e. classes) in the OO computer program that will be eventually created - Hierarchies that structure or rank classes from the more general superclass to the more specialized subclasses (sometimes called inheritance hierarchies) - Generalizations o Group similar types of things like all cars share certain features (e.g. All cars have wheels, engine etc.) - Specializations o Are judgments that categorize different types of things (e.g. Sports car is a special type of car) - A generalization/specialization hierarchy structures things from the general down to the more special o Each class has a more general class above it – a superclass o A class may have a more specialized class below – a subclass - Inheritance: a concept that allows subclasses to share characteristics of their super classes - E.g. a sports car has everything a car has (e.g. 4 wheels and an engine, which it “inherits” from the class car which is above it) - The sports car then specializes o E.g. has a sports option, racing wheels etc. Learning Objectives - Understand the models and processes of defining object-oriented requirements - Develop use case diagrams and activity diagrams - Develop system sequence diagrams - Develop state machine diagrams to model object behaviour - Explain how UML diagrams work together to define functional requirements for the object-oriented approach The System Activities – A Use Case/Scenario View - Use case analysis used to identify and define all business processes that system must support - Use case – an activity a system carried out, usually in response to a user request - Actor o Role played by user o Outside automation boundary Techniques for Identifying Use Cases - Identify user goals o Each goal at the elementary business process (EBP) level is a use case o EBP – task performed by one user in one place and in response to business event that adds measurable business value, and leaves system and data in consistent state - Event decomposition technique (event table) - CRUD analysis technique (create, read/report, update, delete) to ensure coverage
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