IT 352: Information Systems Analysis and Design Use Cases PDF

IT 352: Information Systems Analysis and Design By: Haifa Alhasson 2020 Copyright © 2011 Pearson Education, Inc. Publishing a...

IT 352: Information Systems Analysis and Design By: Haifa Alhasson 2020 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice 11/5/20 Chapter 3 Hall 1 Brief List of Topics Overview of Information System development environment The origin of Software Managing the Information Systems Project Identifying and Selecting Systems Development Projects Initiating and Planning Systems Development Projects Determine the system requirements Structuring System Process Requirements Object-Oriented Analysis and Design Designing Forms and Reports Maintaining Information Systems Copyright © 2011 Pearson Education, Inc. Publishing as Prentice 11/5/20Chapter 2 Hall 2  Modern Systems Analysis and Design Sixth Edition Chapter-7 Appendix A Object-Oriented Analysis and Design: Use Cases  Learning Objectives ü Explain use cases and use case diagrams and how they can be used to model system functionality. ü Discuss process modeling with use cases for electronic commerce application. 4  Use Cases n Use case is a depiction of a system’s behavior or functionality under various conditions as the system responds to requests from users. n Actor is an external entity that interacts with the system. 5  Use Cases (Cont.) FIGURE 7-26 A use case diagram for a university registration system 6  Use Cases (Cont.) n Most actors represent user roles, but actors can also be external systems. n An actor is a role, not a specific user; one user may play many roles, and an actor may represent many users. n A use case model consists of actors and use cases. 7  Use Cases diagrams n Use case diagram: a picture showing system behavior along with the key actors that interact with the system n Abstract use case is when a use case is initiated by another use case. n A use case represents completely functionality. 8  Definitions and Symbols Use Case Actor Boundary Connection Include relationship Extend relationship 9  Definitions and Symbols (Cont.) n Actor is a role, not an individual. ¨ Involved with the functioning of the system at some basic level ¨ Represented by stick figures n Use case represents a single system function. ¨ Represented as an eclipse 10  Definitions and Symbols (Cont.) n System boundary includes all the relevant use cases. ¨ A boundary is the dividing line between the system and its environment. ¨ Use cases are within the boundary. ¨ Actors are outside of the boundary. ¨ Represented as a box 11  Definitions and Symbols (Cont.) n Connection is an association between an actor and a use case. ¨ Depicts a usage relationship ¨ Connection does not indicate data flow ¨ Actors are connected to use cases with lines. ¨ Use cases are connected to each other with arrows. 12  Definitions and Symbols (Cont.) n Extend relationship is an association between two use cases where one adds new behaviors or actions to the other. ¨ Extends a use case by adding new behavior or actions. ¨ Specialized use case extends the general use case. 13  Definitions and Symbols (Cont.) n Include relationship is an association between two use cases where one use case uses the functionality contained in the other. ¨ Indicates a use case that is used (invoked) by another use case. ¨ Links to general purpose functions, used by many other use cases. 14 Definitions and Symbols (Cont.) FIGURE 7-27 A use case diagram featuring an include relationship 15  Written Use Cases n Document containing detailed specifications for a use case n Contents can be written as simple text or in a specified format n Step-by-step description of what must occur in a successful use case 16 FIGURE 7-29 A template for writing use cases (Source: Writing Effective Use Cases by A. Cockburn, © 2001. Adapted by permission of Pearson Education, Inc., Upper Saddle River, NJ 07458.) 17  Level of Use Case n Refers to degree of detail in the use case description n Five suggested levels (Cockburn) 1. White – as seen from clouds 2. Kite – “birds-eye view” 3. Blue – sea-level view summary 4. Fish – below sea-level 5. Black – bottom of the sea detail 18  Sample Format for Written Use Case n Title – descriptive name, matches name in use case diagram n Primary actor – usually a user role n Stakeholders – any group or individual with an interest in the function of the use case 19  Sample Format for Written Use Case (Continued) n Precondition – conditions that must be satisfied in order to execute the use case n Minimal guarantee – outputs that can be expected if the service attempt failed n Success guarantee – outputs that can be expected if the service succeeds 20  Sample Format for Written Use Case (Continued) n Trigger – an event or action that initiates the use case n Main success scenario – description of sequence of interactions between actor and use case during the use case execution n Extensions – detailed description of how errors are dealt with 21 Use case at kite level 22 Use case at sea level Corresponds with Step 1 of kite- level use case 23 Summary n In Appendix A you learned how to: ü Explain use cases and use case diagrams. ü Explain how they can be used to model system functionality. ü Discuss process modeling with use cases for electronic commerce application. 24