1. 1 CS 501 Spring 2002 CS 501: Software Engineering Lecture 9 Techniques for Requirements Definition and Specification I

2. 2 CS 501 Spring 2002 Administration Projects Comments are being sent to each group by email. Should complete today. Teaching Assistants assigned to each project. Will contact you. Observations about Assignment 1 Some projects too ambitious Do not design the project before requirements analysis. Assignment 2 will be posted shortly

3. 3 CS 501 Spring 2002 Assignment 2: What is in a Requirements Document? Remember The requirements document specifies the functionality that you plan to deliver to the client It must be comprehensive and detailed. Everything must be written out -- no hand waving! The requirements document is likely to be several times as long as Assignment 1.

4. 4 CS 501 Spring 2002 Techniques for Requirements Analysis and Definition A variety of tools and techniques. Many are familiar from other courses. There is no correct technique that fits all situations. The craft of requirements analysis and specification is to select the appropriate tool for the particular task. (Other tools are described in Pfleeger, Chapter 4.)

5. 5 CS 501 Spring 2002 Bad Example: Decision Table University Admission Decision Note that the rules are vague. High SATTFFFFF High grades-TFFFF Sports--TTFF Recommendations--TFTF RejectXXX AcceptXXX

6. 6 CS 501 Spring 2002 Good Example: Decision Table University Admission Decision Note that the rules are now specific and testable. SAT > STFFFFF GPA > G-TFFFF Athletics code =  --TTFF Recommendations > A---TFTF Send rejection letterXXX Send acceptance letterXXX

7. 7 CS 501 Spring 2002 Data-Flow Models External entities Processing steps Data stores or sources Data flows

8. 8 CS 501 Spring 2002 Data-Flow Example: University Admissions Applicant Application form Receive application Completed application Evaluate Rejection Acceptance

9. 9 CS 501 Spring 2002 Data-Flow Example: Assemble Application Stage Applicant Application form Receive Completed application Supporting information Pending database Acknowledgment Initiate evaluation Applicant database Evaluation request AND Acknowledgment

10. 10 CS 501 Spring 2002 Data-Flow Example: Process Completed Application Stage Rejection Evaluation Applicant database Evaluation request Acceptance Financial aid Offer Special request

11. 11 CS 501 Spring 2002 Procedural Models: Flowchart Operation Decision Manual operation Report

12. 12 CS 501 Spring 2002 Flowchart: University Admissions Form received New? Database record T Notify student FUpdate database Complete? Notify student T F Evaluate

13. 13 CS 501 Spring 2002 Procedural Models: Pseudo-code Example: Check project plan check_plan (report) if report (date_time) > due_date_time then error (too_late) if report (client) = none then error (no_client) if report (team) max_team then error (bad_team) if error() = none then comments = read_report (report) return (comments (text), comments (grade)) else return error()

14. 14 CS 501 Spring 2002 Entity-Relation Model A Design Methodology for Relational Databases A database of entities and relations Tools for displaying and manipulating entity-relation diagrams Tools for manipulating the database (e.g., as input to database design) Warning: There is much confusion about definitions and notation

15. 15 CS 501 Spring 2002 Entity-Relation Diagram An entity A relation between entities An entity or relation attribute An inheritance relation

16. 16 CS 501 Spring 2002 Example: CS 501 Project Student CS501 Student Major Project 5 to 7 1 Member of Person Client 1 Tech contact 0:n

17. 17 CS 501 Spring 2002 Example: MARC Catalog Record Caroline R. Arms, editor, Campus strategies for libraries and electronic information. Bedford, MA: Digital Press, 1990.

18. 18 CS 501 Spring 2002 MARC Format for Books 001 89-16879 r93 245 Campus strategies for libraries and electronic information 260 {Bedford, Mass.} : Digital Press, c1990. 650 Academic libraries--United States--Automation. 650 Libraries and electronic publishing--United States. 700 Arms, Caroline R. (Caroline Ruth)

19. 19 CS 501 Spring 2002 Entity-Relation Diagram for MARC Book Short title Catalog record Describes Control numb Subject heading Is about Creator Editor of Author of 1:n 1 0:n

20. 20 CS 501 Spring 2002 Data Dictionaries A data dictionary is a list of names used by the system Brief definition (e.g., what is "date") What is it (e.g., number, relation) Where is it used (e.g., source, used by, etc.) May be combined with a glossary As the system is implemented, the data dictionary in the requirements is input to the system data dictionary, which is a formal part of the system specification.

21. 21 CS 501 Spring 2002 A Note on Object Models This course teaches object models as a tool for design. Some people recommend object models for requirements definition, but it is difficult to use them without constraining the system design.

22. 22 CS 501 Spring 2002 Examples For examples of requirements documentation, see the Pfleeger web site: http://www.cs.umd.edu/~sharip/swebook/requirement.html

23. 23 CS 501 Spring 2002 Discussion of Pfleeger, Chapter 4 Format: State a question. Ask a member of the class to answer. (Sorry if I pronounce your name wrongly.) Provide opportunity for others to comment. When answering: Stand up. Give your name or NetID. Make sure the TA hears it. Speak clearly so that all the class can hear.

24. 24 CS 501 Spring 2002 Question 1: Terminology (a)What is the purpose of requirements definition? (b)What is the purpose of requirements specification? (c)What are functional requirements? (d)What are non-functional requirements?

25. 25 CS 501 Spring 2002 Question 2: Static descriptions of requirements (a)What is a static requirements definition? (b)Give two examples of application areas where a static requirements description might be used. (c) How do static definitions of requirement relate to system testing? (d) How do static definitions of requirement relate to system and program design?

26. 26 CS 501 Spring 2002 Question 3: Transition Diagrams (a)What does the book mean by a state? Give an example. (b)What does the book mean by a transition? Give an example. (c)Explain the notation in the expression: f (S i, Cj) = S k Use the following diagram as an example: S1S1 S2S2 S3S3 0 0 0 1 1 1

27. 27 CS 501 Spring 2002 Question 4: Petri Nets Explain the following diagrams: A S1S1 SmSm S S A Event 1 Event n Event A Event 1 Event n..

28. 28 CS 501 Spring 2002 Question 5: Prototyping Requirements (a)How does rapid prototyping differ from other forms of prototyping? (b)Under what circumstances would you use rapid prototyping?