INFO2005 Requirements Analysis Task Scripts

1. INFO2005Requirements Analysis Task Scripts Department of Information Systems

2. Learning Objectives • Present some criticisms of use case concept • Describe OPEN’s task script technique • Locate task scripts within OPEN lifecycle • Understand how to develop simple task scripts

3. What is a Task Script? • A “generic use case” • Ideally defined as one sentence in “SVDPI” form • Subject-Verb-Direct.object-[Preposition-Indirect.object] • Example: • “The salesmanentersthe product number and quantity [tothe Customer Order form]”

4. Task Script vs Use Case • Task scripts are quite similar to use cases • But they also differ in some significant ways

5. Task Script vs Use Case • 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 • By contrast, task scripts:

6. Critique of Use Cases • Use cases represent only interfacebehaviour • Task scripts overcome this limitation:

7. Critique of Use Cases • Use cases are an actual dialogue between user and system • Task scripts overcome this problem

8. Critique of Use Cases • Use cases have no atomicity • Task scripts are organised into trees through task decomposition

9. Critique of Use Cases • Some use case concepts may be confusing • Uses association: • Extends association:

10. Business knowledge Systems knowledge Agent and Task Object Models Business Object Model Implementation Object Model Role in the OPEN Lifecycle Business object identification Language mapping Task scripts are the main technique for this

11. Role in the OPEN Lifecycle • Examination of a single script reveals: • Try this for: “The dealer enters the following data: counterparty, amount, rate, buy-or-sell, special conditions”

12. Role in the OPEN Lifecycle • Each root task corresponds to a responsibility • Analysis of a set of scripts plus “design walkthrough” helps allocate responsibilities to classes in the business object model

13. Developing a Task Script • OPEN task: “Model and re-engineer business processes” • …has subtasks: “Build context (business process) model” “Build task object model”

14. Developing a Task Script “Build task object model” • Business process context model shows:

15. agent actor counterparty auditor message that triggers a task message audit bargain message that triggers a task support system dealer actor enter-deal Developing a Task Script fragment of a Business Process Context Model

16. Developing a Task Script • Each message has: • This is a root task

17. enter-deal commitDeal checkLimits enterDetails checkDealer checkCpty checkGlobal Developing a Task Script fragment of Task Tree for ‘enter deal’

18. Developing a Task Script • Identify any known side scripts • Document on • Textual analysis used to • CRC walkthroughs with

19. Summary • Presented critique of use cases • Described task script technique • Located task scripts in OPEN lifecycle • Seen how to derive a simple task script

20. 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)