HCI of Software. Design Methodologies Tools CASE, UML, Patterns Interface Builders. design. implement

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1 HCI of Software HCI of Software 1 Software (Engineering) is a subset of HCIs (CS/IT professionals are human) and should be experimentally studied. Software is expensive, major cost is human Software costs and production time Software reliability and maintenance requirements design Design Methodologies Tools CASE, UML, Patterns Interface Builders implement verify / validate maintain Program Practice / style Languages, API, Frameworks Software metrics: complexity, effort, KLOC

2 Experimental support for indentation HCI of Software 2 Miara, R.J., Musselman, J.A., Navarro, J.A., Shneiderman, B., Program indentation and comprehensibility, Communications of the ACM, 26, 1983 Experimental Variables indentation space: 0, 2, 4, 6 indentation method: non-blocked indent first line after begin blocked first line flush with begin expertise: novice ( < 3 years), expert ( > 3 years) Dependent Variables comprehension quiz preference rating Task: Study Pascal program (LOC = 102), no comments, no blank lines take quiz, make preference rating Quiz experience significantly better than novice (Surprise!) level of indentation was significant (2 > 4, 6 == 0) Preference Novices more affected by indentation, Blocked preferred

3 Control Flow & Data Structure Documentation HCI of Software 3 Sheniderman, B., Control flow and data structure documentation: two experiments., Communications of the ACM, 25, (search title) Previous work w/ flowcharts had failed to obtain significant results: "...critics cheered our results as justification... adherents found fault and pronounced confidence in their own work..." Program = control flow information + data structure information Exp 1 - program comprehension Experimental Variables (IVs) program + input specifications (IS) program + IS + psuedocode program + IS + data structure graphic Dependent Variables (measurements) comprehension quiz

4 Results F Program + IS 5.06 Program + IS + psuedocode 6.06 * * Program + IS + Data Structure 8.47 * significant p < 0.01 Interpretation HCI of Software 4 More information in psuedocode and data structures than just input specifications. Comparison of psuedocode and data structures is confounded since one is textual and the other is graphic. Mixing both media and information. Need to separate information from media of presentation.

5 Exp 2 HCI of Software 5 Information (DS, CF) by Media (Text, Graphic) A 2 by 2 factorial, between subject design Source Info Media flowchart control flow graphic pseudocode control flow text DS Diagram Data Structure graphic DS Description Data Structure text Results: Text Graphics Data Structure Control Flow Info was significant p < 0.02 Media and Info by Media were non significant Interpretation Source and control flow is redundant information. Data Structure information is new comprehension text Media graphics DS CF

6 GUI: scrollbar by item justification HCI of Software 6 Barnes, G.M. & Kellener, E.K, "Effects of scroll bar orientation and item justification in using list box widgets", Proceedings of the Human Factors and Ergonomics Society 45th Annual Meeting, 2001, pp participants in an Orientation (2) by Justification (3) by Width (2) by Size (2). 3 main (! justification) and all 6 interactions were significant. When item justification matched scroll bar orientation fastest and preferred (significant 2 way interaction). Support for locality (consistency) in UI design: consider task item and task operator.

7 Software Complexity: HCI of Software 7 Understanding, developing, and maintaining software Understanding software is central to: implementation of designs debugging maintenance Understanding software (or design) is a function of its complexity. Complexity can be measured: Structurally absolute Lines of Code relative modules / calls Logically graph # of paths Comprehension is a function of logical flow, programming style, data flow, +...

8 McCabe's Complexity HCI of Software 8 Psychological complexity is a function of the paths (circuits) through a program. Program represented as a graph if directed edges -- cyclomatic number estimates complexity: V(G) = # edges - # nodes + 2 ( # connected components) V(G) is approximated well by the number of logical predicates (tests) in a program. Program path changes only on a logical predicate. V(G) measures modularity: 3-7 good design + 10 needs to be decomposed V(G) correlates w/ programmers rating of code.

9 Halstead's Software Science HCI of Software 9 A program's complexity should be measured from its components (like reading) Halstead determined several measures of software from: n1 n2 N1 N2 number of unique operators number of unique operands frequency of operators frequency of operands program's vocabulary implementation length volume (V) = N (log 2 n) (n) = n1 + n2 (N) = N1 + N2 // bits to represent volume could be estimated from program specification effort (E) = V (n1 / n2) (N2 / 2) Halstead predicted time to complete programs from specs w/in 12% (for assembler solns)

10 Similarity among software metrics HCI of Software 10 Numerous software metrics have been developed in response to McCabe and Halstead. There exist tools that measure requirements, specifications and software complexity. Curtis, B., Sheppard, S.B., Milliman, P., Borst, M.A., Love, T., Measuring the Psychological Complexity of Software Maintenance Tasks with the Halstead and McCabe Metrics. IEEE Transactions on Software Engineering, 1979, pp ccorrelated Halstead's Effort, McCabes V(G), and Lines of Code (LOC) E V(G) V(G).84* LOC.97 *.64* * p < Jensen & Vairavan ('85) looked at real-time software complexity. They found correlations between E and V(G) in the range of.70 to.92 across 5 sets of programs from different sources.

11 OOP Metrics HCI of Software 11 Comparing software complexity measures in an OOP language (Actor): ActQOOL (Barnes and Swim, Journal of Object Oriented Programming, 1993) LOC Volume Length V(G) Self Others Methods Volume Length V(G) Self Others Methods Variables Self and Others are counts of messages sent to self or other methods Methods and Variables are counts of local methods and variables in a class

12 ActQOOL HCI of Software 12 SmallTalk like browser for code editing that also visually displayed software metrics. For example IndexedCollection a subclass of Collection Class/Ancestor Syntax-Based Metrics: num of lines 115/553

13 Fisheye software views HCI of Software 13 Jakobsen, M.R, & Hornbæk, K., Evaluating a Fisheye View of Source Code, Proceedings CHI 2006, Fisheye view Vs. common, linear presentation of source code. 16 participants performed some tasks significantly faster with the fisheye view (complex results), and significantly preferred fisheye view.

14 I. Goldman's 3D program visualizer (2002) 3D program visualization devices 14

15 3D programming language devices 15 M.A. Najork S.M. Kaplan, 1991, The CUBE Language

16 Visual programming devices 16 Alice, Scratch (Snap!), Kodu game lab, App Inventor Represents classes, methods (block code selection from drop down lists)/ No syntax errors possible.

17 HCI of Software 17 Software can be measured & experimental software engineering can be done! Convergent evidence in Software Engineering career / practice case studies expert opinions controlled studies Renewed interest in empirical research. Where is the science in Computer Science? naturalistic naturalistic anecdotal / introspective hypothesis testing How do you think the HCI of software design, development, verification, validation, and documentation can be: improved?? studied??

18 Related References HCI of Software 18 Binkley, D., Gold, N., Harman, M., An Empirical Study of Static Program Slice Size, ACM Transactions on Software Engineering and Methodology,Vol. 16, No. 2, Article 8, Publication date: April Brandt, P.J., Lewenstein, J., Dontcheva, M., Klemmer, S.R., Two Studies of Opportunistic Programming: Interleaving Web Foraging, Learning, and Writing Code, CHI 2009, (search title) Murray, A., Lethbridge, T.C., On generating cognitive patterns of software comprehension, CASCON '05 Proceedings, 2005, (search title) Myers, Brad and Ko, Andrew, The Past, Present and Future of Programming in HCI (2009). Institute for Software Research. Paper Rosson, M.B., Human Factors in Programming and Software Development, ACM Computing Surveys, Vol. 28, No. 1, March (search title)