After this chapter the student should have acquired the following knowledge and skills: Typical system requirements and problems, five problem frames: Transformation, simple workpieces, required behavior, information display, commanded behavior. | Methods for Requirements Engineering Lecture-30 Recap 2 Requirement Engineering in AMs XP Customer involvement Requirement scenarios Changes/Refactoring Testing Requirement methods System models Today’s lecture 3 Methods for requirement engineering Class definition An implementation of an object type The object type Bank Customer refers to a class of bank customers Objects that share common attributes and operations An object is an instance of a class For example, if “John Smith” is a bank customer, then bank customer is the class and “John Smith” is an instance of the bank customer Operations and methods Used to read and manipulate the data of an object Reference only the data structures of that object type To access the data structures of another object, objects must send messages to that object Methods specify the way in which operations are encoded in software Encapsulation Packaging together of data and operations that manipulate the data Details of how the operation is performed | Methods for Requirements Engineering Lecture-30 Recap 2 Requirement Engineering in AMs XP Customer involvement Requirement scenarios Changes/Refactoring Testing Requirement methods System models Today’s lecture 3 Methods for requirement engineering Class definition An implementation of an object type The object type Bank Customer refers to a class of bank customers Objects that share common attributes and operations An object is an instance of a class For example, if “John Smith” is a bank customer, then bank customer is the class and “John Smith” is an instance of the bank customer Operations and methods Used to read and manipulate the data of an object Reference only the data structures of that object type To access the data structures of another object, objects must send messages to that object Methods specify the way in which operations are encoded in software Encapsulation Packaging together of data and operations that manipulate the data Details of how the operation is performed hidden from user Prevents the unauthorised access of an object’s data Inheritance Objects at a lower level in class hierarchy inherit the operations and attributes of their parent(s) Objects are able to incorporate data and/or operations specific to themselves Inherits data from more than one parent is called multiple inheritance. Illustration of object concepts Messages Objects communicate by sending messages Message comprises: Name of receiver object Operation to be invoked Optional set of parameters When an object receives a message it causes an operation to be invoked The operation performs the appropriate method Message passing Object modelling - Library example A library system is intended to provide its users with the ability to automate the process of: Acquiring library items Cataloguing library items Browsing library items Loaning library items Library items comprise published and recorded material The system will be administered by a member of the library staff Users must .
