1. CS 5150 Software Engineering
Lecture 8
Requirements 1

2. Administration Assignment 1: see the Assignments page on the web site
Due Friday at 11:00 p.m. Submit by .
• Feasibility study (group assignment)
Remember to send a copy to your client
• Survey (individual assignment)
Test 1
Uncollected answer books are at the reception at 301 College Avenue

3. Administration Assignment 2
Presentations will be on October 14 to 16. See the available times on the home page of the web site.
• Sign up now.
• Client must be able to attend.
• Not all members of the project team need attend.
More information about the presentations will be given in a later class.

4. Test 1: Visibility Question: How does your process provide visibility?
Objective: Keep everybody informed of the progress
• client, management (instructor + TA), colleagues in team
Visibility has many aspects
• sequential processes have intermediate deliverables; iterative processes have visible products after each iteration
• presentations and reports are visible milestones
• schedules, progress reports, and team meetings keep track
of progress between major milestones

5. From Test 1: Process Steps
A company that maintains airplane wishes to provide every
technician with a hand held computer and software.
(i) How much should the choice of technology be considered during the feasibility study?
(ii) In how much detail should the choice of technology be specified during the requirements phase of the project?
(iii) At what stage should the decision be made to use a Panasonic Toughbook with Windows Mobile?

6. Test 1: Process Steps (answer)
How much should the choice of technology be considered during the feasibility study?
During the feasibility study it is important to know that the project is technically feasible.
This can be achieved by identifying one possible technical approach and analyzing it sufficiently to show that it is capable of fulfilling the requirements of the system. It can also be used to estimate costs of hardware, software, etc.
However, this is only a possible approach. When the system design is carried out in detail, totally different technology may be chosen.

7. Test 1: Process Steps (answer)
In how much detail should the choice of technology be specified during the requirements phase of the project?
A requirement is a statement of need as expressed by a client.
The client's requirements are that the system performs various functions, e.g., collects certain data, saves it, displays it, performing calculations, etc.
The decision to use specific equipment or software is usually not a requirement of the client. It comes later, as part of the design.

8. Test 1: Process Steps (answer)
At what stage should the decision be made to use a Panasonic Toughbook with Windows Mobile?
This is a design decision. It is part of the system design.

9. Why are Requirements Important?
Causes of failed software projects (Standish Group study, 1994)
Incomplete requirements 13.1%
Lack of user involvement 12.4%
Lack of resources 10.6%
Unrealistic expectations 9.9%
Lack of executive support 9.3%
Changing requirements & specifications 8.8%
Lack of planning 8.1%
System no longer needed 7.5%
The commonest mistake is to build the wrong system.

10. Requirements in Iterative Refinement
Evaluation/acceptance
Requirements
Design
Implementation

11. Requirements in the Modified Waterfall Model
The requirements need continual updating as the project continues.
Feasibility study
Requirements
System design
Program design
Implementation (coding)
Testing
Acceptance & release
Operation & maintenance

12. Goals during the Requirements Phase
• Understand the requirements in detail.
• Specify the requirements in a manner that is clear to the client. Ensure that the client understands the description of the requirements and their implications.
• Specify the requirements in a manner that is clear to the people who will design and implement the system.
The list of requirements in the Requirements Documentation
may be the basis for acceptance testing of the final system

13. Stages in the Requirements Phase
Requirements define the function of the system from the
client's viewpoint.
This phase can be divided into:
• Analysis to establish the system's services, constraints and goals by consultation with users.
Modeling to organize the requirements in a systematic and comprehensible manner.
Specification in a manner and level of detail that is understandable by both client and development staff.

14. The Requirements Process
Analysis
Feasibility
Study
Requirements
Modeling
Requirements
Specification
Feasibility
Report
Work with the client to understand the requirements
Organize the requirements in a systematic and comprehensible manner
Documentation of
Requirements
Analysis Report (optional)

15. Requirements Analysis
High-level abstract description of requirements:
• Specifies external system behavior
• Comprehensible by customer, management and users
Should reflect accurately what the client wants:
• Services that the system will provide
• Constraints under which it will operate
Often described in a separate report for consultation with the client.
"Our understanding of your requirements is that ..."

16. Requirements Analysis: Interviews with Clients
Client interviews are the heart of the requirements analysis and definition.
Clients may have only a vague concept of requirements.
• Allow plenty of time.
• Prepare before you meet with the client
• Keep full notes
• If you do not understand, delve further, again and again
• Repeat what you hear
• Small group meetings are often most effective

17. Requirements Analysis: Stakeholders
Identify the stakeholders:
Who is affected by this system?
Client
Senior management
Production staff
Computing staff
Customers
etc., etc., etc.,
Example: Andrew project (Carnegie Mellon and IBM)

18. Requirements Analysis: Stakeholders & Viewpoint Analysis
Viewpoint Analysis. Analyze the requirements as seen by each group of stakeholders
Example: University Admissions System
• Applicants
• University administration
Admissions office
Financial aid office
Special offices (e.g., athletics, development)
• Academic departments
• Computing staff
Operations and maintenance

19. Requirements Analysis: Understand the Requirements
Understand the requirements in depth:
• Domain understanding
Example: Philips light bulbs
• Understanding of the real requirements of all stakeholders
Stakeholders may not have clear ideas about what they require, or they may not express requirements clearly.
They are often too close to the old way of doing things.
• Understand the terminology
Clients often use specialized terminology that they think you understand.

20. Requirements Analysis: Understand the Requirements
Understanding the requirements may need studies:
Market research
focus groups, surveys, competitive analysis, etc.
Example: Windows XP T-shirt
Technical evaluation
experiments, prototypes, etc.
Example: Windows XP boot faster

21. Requirements Analysis: Understand the Requirements New and Old Systems
In requirements analysis it is important to distinguish:
• features of the current system
• proposed new features
Clients often confuse the current system with the underlying requirement.
A new system is when there is no existing system.
A replacement system (or subsystem) is when a system is built to replace an existing system.
A legacy system is an existing system that is not being replaced, but must interface to the new system.

22. Requirements Analysis: Conflicts
Recognize and resolve conflicts
(e.g., functionality v. cost v. timeliness)
Example: Dartmouth general ledger system

23. Requirements Analysis: Conflicts Negotiation with the Client
Sometimes the client will request some functionality that is very
expensive or impossible. What do you do?
• Talk through the requirement with the client. Why is it wanted? Is there an alternative that is equivalent?
• Explain the reasoning behind your concern. Explain the technical, organizational, and cost implications.
• Be open to suggestions. Is there a gap in your understanding? Perhaps a second opinion might suggest other approaches.
Before the requirements phase is completed the client and
development team must resolve these questions.

24. Functional Requirements
Functional requirements describe the functions that the system must perform. They are identified by analyzing the use made of the system:
• Functionality
• Data
• User interfaces
Analyzing and specifying the functional requirements is the theme of the next two lectures.

25. Non-Functional Requirements
Requirements that are not directly related to the
functions that the system must perform
Product requirements
performance, reliability, portability, etc...
Organizational requirements
delivery, training, standards, etc...
External requirements
legal, interoperability, etc...
Marketing and public relations
Example: In the NSDL, the client (the National Science Foundation) wanted a system that could be demonstrated by the end of 2002

26. Example of Non-Functional Requirements
Example: Library of Congress Repository
Use technology that the client's staff are familiar with:
Hardware and software systems (IBM/Unix)
Database systems (Oracle)
Programming languages (C and C++)
Recognize that the client is a federal library:
Regulations covering government contracting, accessibility to people with disabilities, etc.
Importance of developing a system that will be respected by other major libraries

27. Unspoken Requirements
Examples:
Resistance to change
Departmental friction
Management strengths and weaknesses
Discovering the unspoken requirements is often the most difficult part of developing the requirements.

28. Realism and Verifiability
Requirements must be realistic, i.e., it must be possible to meet them.
Wrong: The system must be capable of x (if no known computer system can do x at a reasonable cost).
Requirements must be verifiable, i.e., it must be possible to test whether a requirement has been met.
Wrong: The system must be easy to use.
Right: After one day's training an operator should be able to input 50 orders per hour.

29. Evolution of Requirements
• If the requirements definition is wrong, the system will be
wrong.
• With complex systems, understanding of requirements
always continues to improve.
Therefore...
• The requirements definition must evolve.
• Its documentation must be kept current (but clearly
identify versions).