1. 1 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. http://marketing.blogs.ie.edu/archives/2007/10/usability_and_d.php CSSE 477 – Intro to Usability Bass’s perspective

2. 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. http://www.cs.cmu.edu/~bej/usa/people.html

3. 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. 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 After this, you’ll have a full grip on Bass… Not this Bass… For Quiz question 1, see slide 8 !

5. 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?supplementary spec template What is Usability “about” – Ch 4? What are some good tactics – Ch 5? Or this Bass…

6. 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. 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. 8 Which brings up – How do you “tuna” Bass? Not even a little bass. Quiz question 1

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

10. 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. 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 Ch 5 And that’s him! Quiz questions 4, 5 Bass’s CMU colleague, and our demo…