CSSE 477 – Intro to Usability Bass’s perspective

1. CSSE 477 – Intro to UsabilityBass’s perspective Steve Chenoweth Tuesday, 10/25/11 Week 8, Day 2 Right – Desktop computer usability metaphor, from http://marketing.blogs.ie.edu/archives/2007/10/usability_and_d.php.

2. Today • How’s Project 6 going?… • Software usability from Bass’s perspective – this  • SA Ch 4, pp 90-93 (Usability scenarios) & Ch 5, pp. 121-123 (Usability tactics) • Lots and lots in the ID book, which we talked from yesterday • Bass is an expert on usability and architecture. See publications at http://www.cs.cmu.edu/~bej/usa/people.html.

3. Coming up… Thursday: Lots of time to work on the project, Friday: Status on project 6 (w poss extension) Last biweekly quiz Next week: Service-oriented architectures!

4. We last pick usability from Bass’s QA list… • Bass’s list of six, from the inside back cover of his book: • Availability • Modifiability • Performance • Security • Testability • Usability Not this Bass… After this, you’ll have a full grip on Bass… For Quiz question 1, see slide 8 !

5. What’s Bass say about this QA? • Problem – How easily can a user accomplish a desired task? This needs to be attacked systematically: • E.g., a consistent user interface • Architectural choices about what data is available when & where • Goals – Both efficiency and effectiveness • For “heads down users” – time is money • For “power users” – can they do novel / infrequent things? • Motivation – The system is often sold based on gains in user efficiency or effectiveness • Scenarios – What’s in “The Notes” at the end of the supplementary spec template? • What is Usability “about” – Ch 4? • What are some good tactics – Ch 5? Or this Bass…

6. Bass’s usability scenarios • Source: end user • Stimulus: wish to learn/use/minimize errors/adapt/feel comfortable • Artifact: system • Environment: configuration or runtime • Response: provide ability or anticipate • Measure: task time, number of errors, user satisfaction, efficiency Or this Bass… Quiz question 2

7. Example scenario • Source: Users • Stimulus: Minimize impact of errors • Artifact: System • Environment: At runtime • Response: Wishes to cancel current operations • Response Measure: Cancellation takes less than one second Heavens! Not this Bass… Quiz question 3

8. Which brings up – How do you “tuna” Bass? Not even a little bass. Quiz question 1

9. Usability situations A runtime attribute: • Learning • Using efficiently • Minimizing errors • Adapting to user needs • Increasing confidence and satisfaction Probably too optimistic To be a software architect. (Lance Bass of ‘N Sync.) Ch 4

10. Tactics to achieve usability Strategies: • Design time • Separate UI from rest of system [sound familiar?] • Client / server • Model-view-controller • Presentation-abstraction-control • Seeheim and Arch/Slinky – See http://www.cs.cmu.edu/~bej/usa/publications/OOPSLA-Patterns.pdf. • Runtime • Support user initiative • Cancel, Undo – “usability commands” • System must “listen” for these • Can’t be blocked by ongoing actions • Feedback on what’s happening • Support system initiative • User/System/Task models (that’s 3 different ones!) • What is the user expecting to happen? • Predict user intent or response • Encapsulating such things, so as to change the models easily • Tailoring dynamically based on past user behavior Bass’s CMU colleague, and our demo… And that’s him! Ch 5 Quiz questions 4, 5