5 Chapter 5: Modeling Systems Requirements: Events and Things Systems Analysis and Design in a Changing World, 3rd Edition 5 Learning Objectives Explain the many reasons for creating information system models Describe three types of models and list some specific models used for analysis and design Explain how events can be used to define system requirements Identify and analyze events to which a system responds Recognize that events trigger system activities or use cases Systems Analysis and Design in a Changing World, 3rd Edition 2 5 Learning Objectives (continued) Explain how the concept of things in the system also defines requirements Explain the similarities and the differences between data entities and objects Identify and analyze data entities and objects needed in the system Read, interpret, and create an entity-relationship diagram Read, interpret, and create a class diagram Systems Analysis and Design in a Changing World, 3rd Edition 3 5 Overview Document functional requirements by creating models Models created during analysis phase activity: Define system requirements Two concepts define system requirements in traditional approach and object-oriented approach Events Things Systems Analysis and Design in a Changing World, 3rd Edition 4 5 Models and Modeling Analyst describes information system requirements using a collection of models Complex systems require more than one type of model Models represent some aspect of the system being built Process of creating model helps analyst clarify and refine design Models assist communication with system users Systems Analysis and Design in a Changing World, 3rd Edition 5 5 Reasons for Modeling Systems Analysis and Design in a Changing World, 3rd Edition 6 5 Types of Models Different types of models are used in information systems development Mathematical - formulas that describe technical aspects of the system Descriptive - narrative memos, reports, or lists that describ