Handwritten Text Recognition for manuscripts and early printed texts
Unit V.pptx
1. Unit V: HCI in the System
Process
LESSON 01: THE SOFTWARE LIFECYCLE
2. HCI in the System Software
Software engineering and the design process for interactive systems
Usability engineering
Iterative design and prototyping
Design rationale
3. The Software Lifecycle
Software engineering is the discipline for understanding the software design
process, or life cycle.
Designing for usability occurs at all stages of the life cycle, not as a single isolated
activity.
5. Activities in the Life Cycle
Requirements Specification
designer and customer try capture what the system is expected to provide can be expressed in
natural language or more precise language, such as a task analysis would.
Architectural Design
High level description of how the system will provide the services required factor system into
major components of the system and how they are interrelated needs to satisfy both functional
and non-functional requirements.
Detailed Design
Refinement of architectural components and interrelations to identify modules to be implemented
separately the refinement is governed by the non-functional requirements.
6. Verifications and Validations
Verification
Designing the product right.
Validation
Designing the right product
The Formerly Gap
Validation will always rely to some extent on subjective
means of proof.
Management and Contractual Issues
Design in commercial and legal contexts.
8. Usability Engineering
The ultimate test of usability based on measurement of user experience
Usability engineering demands that specific usability measures be made explicit as requirements.
Usability Specification:
Usability attribute/principle
Measuring content
Measuring method
Now level/ worst case/ planned level/ best level
Problems
Usability specification requires level of detail that may not be possible early in design
Satisfying a usability specification does not necessarily satisfy usability.
10. ISO Usability Standard 9241
Adopts traditional usability categories:
Usability
- The effectiveness, efficiency and satisfaction with which specified users achieve specified goals in
particular environments
Effectiveness
- The accuracy and completeness with which specified users can achieve specified goals in particular
environment.
Efficiency
- The resources expended in relation to the accuracy and the completeness of goals achieved.
Satisfaction
- The comfort and acceptability of the work system to its users and other people affected by its use.
12. Criteria by which measuring method can
be Determined
Time to complete the task
Percent of task complete
Percent of task completed per unit time
Ratio of successes to failure
Time spent in errors
Percent or number of errors
Percent or number of competitors better than it
Number of commands used
Frequency of help and documentation use
Percent of favourable/unfavourable user
comments
Number of repetitions of failed commands
Number of runs of successes and of failures
Number of times interface mislead the user
Number of good and bad features
Numbers of available commands not invoked
Number of regressive behaviors
Numbers of users preferring your system
Number of times users need to work around a
problem
Number of times user losses control of the
system.
13. Iterative design and Prototyping
Overcomes inherent problems of incomplete requirements
Prototype
- Simulate or animate some features of intended systems
- Different types of prototype
--Throw-away
--Incremental
--Evolutionary
Management issues
- Time
- Planning
- Non-functional
- contracts
14. Techniques for Prototyping
Storyboards – needs not be computer based and can be animated.
Limited Functionality Simulations – some part of systems functionality provided by
designers tools like HyperCard are common for these Wizard Oz technique.
Warning about iterative design
Design inertia – early bad decisions stay bad
Diagnosing real usability problems in prototypes and not just the symptoms.
15. Design Rationale
Design Rationale is information that explains why a computer system is the way it
is.
Types of DR
Process oriented – preserves order of deliberation and decision-making
Structure-Oriented – emphasizes post hoc structuring of considered desired
alternatives
- Example
- - Issue-based information system (IBIS)
- Design space analysis
16. Issue-based Information System
Based for much of design rationale research
Process oriented
Main elements
Issues – hierarchical structure with one ‘root’ issue.
Positions – potential resolutions of an issue
Arguments – modify the relationship between position and issues.
Gibis is a graphical version.
18. Design Space Analysis
Structure- oriented
QOC – hierarchical structure
DRL – similar to QOC with a larger language and more formal semantics.
20. Psychological Design Rationale
To support task-artefact cycle in which user tasks are affected by the systems they
use.
Aims to make explicit consequences of a design for users.
Designers identify tasks system will support.
Scenarios are suggested to test task.
Users are observed on systems
Psychological claims of system made explicit
Negative aspects of design can be used to improve next iteration of design.