This document discusses human-computer interaction in the software development process. It covers topics like the software life cycle, prototyping, design rationale, and usability engineering. Specifically, it describes the waterfall model of the software development life cycle, including requirements specification, architectural design, detailed design, coding, integration and testing, verification and validation, and maintenance. It also discusses prototyping approaches like throwaway, incremental, and evolutionary prototyping. Design rationale techniques like issue-based information systems and design space analysis are explained. Finally, it defines usability engineering as a discipline focused on improving the usability of interactive systems.

1. CS8079 - Human
Computer Interaction
UNIT - II
DESIGN & SOFTWARE PROCESS
Year: IV
Semester: VII
Date: 14-09-2020
Prepared by,
Mrs.T. SUGANYA, M.E.,

2. Topics
 HCI in Software Process
◦ Software Life Cycle
◦ Prototyping in Practice
◦ Design Rationale
◦ Usability Engineering

3. SDLC – Waterfall Model
 Waterfall Model provides a good starting
point for discussing the logical flow of
activity
1. Activities in the life cycle
2. Validation &Verification
3. Management & Contractual Issues
4. Interactive Systems & Software Life Cycle

4. SDLC – Waterfall Model
1. Activities in the life cycle
 Requirement Specification:
 What the system is supposed to do?
 Customer and designer involved
 Capture the description
 Elicit the information about the
Environment - in which it will function
 Formulate requirements in Language
suitable for development

6. SDLC – Waterfall Model
 Architectural Design:
◦ How the System Provides services?
◦ Decompose the system into components
◦ Determine which component for which service
 Detailed Design:
◦ Refinement of the component
◦ Choosing best refinement(optimization)
 Try to satisfy many of the non functional requirements
 Coding & UnitTesting
◦ Implement – Programming Language
◦ Test the components - Units

7. SDLC – Waterfall Model
 Integration &Testing
◦ Integrate the components described in
architectural design & test it
◦ AcceptanceTesting – Customer
◦ After acceptance, release the product
◦ Certify the final system
 Maintenance
◦ Correction of errors discovered after release
◦ Revise the requirements

8. SDLC – Waterfall Model
2.Verification &Validation
 Verification
 process of checking that a software achieves its
goal without any bugs.
 product that is developed is right or not
 Are we building the product right?
 Validation
 it satisfies all the customer's stated and implied
needs
 Are we building the right product?

9. SDLC – Waterfall Model

10. SDLC – Waterfall Model
 Gap Analysis
◦ Need Abstract Model to bridge the gap

11. SDLC –Waterfall Model
3. Management & Contractual Issues
 Managerial Issues
 Time Constraints
 Economic forces
4. Interactive System
& Software Life cycle
Lot of Feedbacks
required to refine
/improve the system

12. Prototyping in Practice
 Prototype Mock up or Model or draft version
 Iterative Design
◦ Overcomes the problem of incomplete
requirements specifications
◦ Process of designing a product in which the
product is tested and evaluated
repeatedly at different stages of design
◦ Incrementally improves final product
◦ Described by prototype
 3 Approaches
◦ Throw away
◦ Incremental
◦ Evolutionary

13. Prototyping in Practice
The process of prototyping involves the following steps
Identify basic requirements
• Determine basic requirements including the input and
output information desired. Details, such as security, can
typically be ignored.
2.Develop initial prototype
• The initial prototype is developed that includes only user
interfaces.
3. Review
• The customers, including end-users, examine the
prototype and provide feedback on potential additions
or changes.
4.Revise and enhance the prototype
• Using the feedback both the specifications and the
prototype can be improved.

14. Prototyping in Practice

15. Prototyping in Practice
 Software prototype

16. Prototyping Approaches
 Throw away
◦ Prototype is build andTested
◦ Knowledge gained from exercise is used to
build the final product
◦ Actual prototype is discarded when the goal is
achieved

17. Steps:
 Write preliminary requirements
 Design the prototype
 User experiences/uses the prototype,
specifies new requirements
 Repeat if necessary
 Write the final requirements

18.  Incremental
◦ Overall product is partitioned into independent
and smaller components
◦ Build the prototype for each component and
merge all prototypes
◦ Final product is released as a series of products
◦ the time gap between user and software
developer is reduced.

19.  Evolutionary
 Prototype is build andTested
 Actual prototype is not discarded- Basis for the
iteration of design
 builds only the requirements that are well
understood
 Modifications made to the system

20. Techniques &Tools for Prototyping
 Story Board
◦ Snapshots of the interface
◦ Annotations, script
◦ Limited functionality simulation
 Simulation
◦ HyperCard
 Combines a flat-file database with a graphical,
flexible, user-modifiable interface.
 includes a built-in programming
language called HyperTalk for manipulating data and
the user interface.

21. Design Rationale
 What?
◦ Information describes
 Structure of a system
 Functionality/Behavior of a system
 Types of DR:
◦ Process-oriented
 preserves order of deliberation and decision-
making
◦ Structure-oriented
 emphasizes post hoc structuring of considered
design alternatives
 Two examples:
◦ Issue-based information system (IBIS)
◦ Design space analysis

22. Process-oriented
Main elements:
o Issues
hierarchical structure with one ‘root’
issue
o Positions
Potential resolutions of an issue
o Arguments
modify the relationship between
positions and issues
Eg: Login Form – Issue :Authenticated
User

24. Design Space Analysis
Questions, options, criterion (QOC)
Eg: Ride booking Application- Q: to, from, No. of persons
Option : Km , Criteria (No. of km : price)

25. Usability Engineering
 What?
◦ is a professional discipline
◦ focuses on improving the usability of
interactive systems
◦ Usability
◦ capacity of a system to provide a condition for
its users to perform the tasks safely, effectively,
and efficiently

26. Usability Engineering