1. Requirements Analysis 16. 1 Analysis Patterns - 2005b516.ppt © Copyright De Montfort University 2000 All Rights Reserved INFO2005 Requirements Analysis Task Scripts Department of Information Systems

2. Requirements Analysis 16. 2 Analysis Patterns - 2005b516.ppt © Copyright De Montfort University 2000 All Rights Reserved Learning Objectives v Present some criticisms of use case concept v Describe OPEN’s task script technique v Locate task scripts within OPEN lifecycle v Understand how to develop simple task scripts

3. Requirements Analysis 16. 3 Analysis Patterns - 2005b516.ppt © Copyright De Montfort University 2000 All Rights Reserved What is a Task Script? v A “generic use case” v Ideally defined as one sentence in “SVDPI” form – Subject-Verb-Direct.object-[Preposition- Indirect.object] v Example: –“The salesman enters the product number and quantity [to the Customer Order form]”

4. Requirements Analysis 16. 4 Analysis Patterns - 2005b516.ppt © Copyright De Montfort University 2000 All Rights Reserved Task Script vs Use Case v Task scripts are quite similar to use cases v But they also differ in some significant ways

5. Requirements Analysis 16. 5 Analysis Patterns - 2005b516.ppt © Copyright De Montfort University 2000 All Rights Reserved Task Script vs Use Case v Use cases : –represent only behaviour at the user / system interface –are an actual dialogue between user and system –are not fully OO, conceptually or notationally v By contrast, task scripts:

6. Requirements Analysis 16. 6 Analysis Patterns - 2005b516.ppt © Copyright De Montfort University 2000 All Rights Reserved Critique of Use Cases v Use cases represent only interface behaviour v Task scripts overcome this limitation:

7. Requirements Analysis 16. 7 Analysis Patterns - 2005b516.ppt © Copyright De Montfort University 2000 All Rights Reserved Critique of Use Cases v Use cases are an actual dialogue between user and system v Task scripts overcome this problem

8. Requirements Analysis 16. 8 Analysis Patterns - 2005b516.ppt © Copyright De Montfort University 2000 All Rights Reserved Critique of Use Cases v Use cases have no atomicity v Task scripts are organised into trees through task decomposition

9. Requirements Analysis 16. 9 Analysis Patterns - 2005b516.ppt © Copyright De Montfort University 2000 All Rights Reserved Critique of Use Cases v Some use case concepts may be confusing v Uses association: v E xtends association:

10. Requirements Analysis 16. 10 Analysis Patterns - 2005b516.ppt © Copyright De Montfort University 2000 All Rights Reserved Role in the OPEN Lifecycle Agent and Task Object Models Business Object Model Implementatio n Object Model Business knowledge Systems knowledge Business object identification Language mapping Task scripts are the main technique for this

11. Requirements Analysis 16. 11 Analysis Patterns - 2005b516.ppt © Copyright De Montfort University 2000 All Rights Reserved Role in the OPEN Lifecycle v Examination of a single script reveals: v Try this for: “The dealer enters the following data: counterparty, amount, rate, buy-or-sell, special conditions”

12. Requirements Analysis 16. 12 Analysis Patterns - 2005b516.ppt © Copyright De Montfort University 2000 All Rights Reserved Role in the OPEN Lifecycle v Each root task corresponds to a responsibility v Analysis of a set of scripts plus “design walkthrough” helps allocate responsibilities to classes in the business object model

13. Requirements Analysis 16. 13 Analysis Patterns - 2005b516.ppt © Copyright De Montfort University 2000 All Rights Reserved Developing a Task Script v OPEN task: “Model and re-engineer business processes” v …has subtasks: “Build context (business process) model” “Build task object model”

14. Requirements Analysis 16. 14 Analysis Patterns - 2005b516.ppt © Copyright De Montfort University 2000 All Rights Reserved Developing a Task Script “Build task object model” v Business process context model shows:

15. Requirements Analysis 16. 15 Analysis Patterns - 2005b516.ppt © Copyright De Montfort University 2000 All Rights Reserved Developing a Task Script fragment of a Business Process Context Model counterparty enter-deal audit auditor dealer bargain actor agentmessage support system actor message that triggers a task

16. Requirements Analysis 16. 16 Analysis Patterns - 2005b516.ppt © Copyright De Montfort University 2000 All Rights Reserved Developing a Task Script v Each message has: v This is a root task

17. Requirements Analysis 16. 17 Analysis Patterns - 2005b516.ppt © Copyright De Montfort University 2000 All Rights Reserved Developing a Task Script enter-deal checkDealer checkCpty checkGlobal enterDetails checkLimits commitDeal fragment of Task Tree for ‘enter deal’

18. Requirements Analysis 16. 18 Analysis Patterns - 2005b516.ppt © Copyright De Montfort University 2000 All Rights Reserved Developing a Task Script v Identify any known side scripts v Document on v Textual analysis used to v CRC walkthroughs with

19. Requirements Analysis 16. 19 Analysis Patterns - 2005b516.ppt © Copyright De Montfort University 2000 All Rights Reserved Summary v Presented critique of use cases v Described task script technique v Located task scripts in OPEN lifecycle v Seen how to derive a simple task script

20. Requirements Analysis 16. 20 Analysis Patterns - 2005b516.ppt © Copyright De Montfort University 2000 All Rights Reserved Further Reading www.open.org Graham, I., 1995, “Migrating to Object Technology” Addison-Wesley (this describes the earlier SOMA methodology, in which task scripts were first used) Graham, I., et al, 1997, “The OPEN Process Specification” Addison-Wesley (particularly pp 89-90 & 236-248) Graham, I., 1998, “Requirements Engineering and Rapid Development” Addison-Wesley (particularly pp 138--154 and Appendix B)