1. Visualizing non-functional requirements

• • Neil Ernst and Yijun Yu and John Mylopoulos

• [email_address]

2. Overview

Many visualization techniques

Most focus on functional artifacts

• code, design, architecture, requirements

Move visualization towards problem-solving rather than problem representation

Use non-functional system qualities usability, security, trust, performance to represent goals users have in analyzing a system

3. Context

Inspiration: Performance visualization

• Use colour to show performance impact of cache optimizations

Expand on existing softgoal/NFR support in the i* modeling tool, OpenOME

4. 5. Goal evaluation

Assign criteria to certain goals, and try to reason about cascading effects

Several algorithms for reasoning about a goal model

We chose an algorithm for bottom-up reasoning

6. 7. NFR Evaluation

4 NFRs analyzed

• certainty how confident is the modeler that a soft-goal will be achieved?

• feasibility degree of deniability, likelihood of not being accomplished inverse deniablility

• trustability assigned value based on actor relationships (end of chain trust future work)

• performance assigned by modeler by assessing task goals, relative to other goals

8. Visualizing NFRs

2 approaches: operationalize or orthogonalize

Use visual variables (Bertin83):

9. Bertin's visual variables from:http://www.math.yorku.ca/SCS/Gallery/images/bertin-ve.jpg 10. 11. 12. Evaluation

No completed user testing

Used cognitive dimensions [Green89] as heuristic walkthrough

Fairly strong in viscosity, secondary notations, hard mental operations can use the diagram for scenario evaluation, weighing of options

Challenges are in scalability and abstraction

Limited visual variables (look at size, position, shape, texture/pattern)

13. Future work

Add an algebra for composing and abstracting relationships

Difficult to quantify some NFRs accurately, e.g. usability

Empirical usability testing

Currently working on using Eclipse technologies e.g. GEF/GMF to visualize conceptual models

14. References

[Green89] - Green, T.R.G.Cognitive dimensions of notations . In People and Computers V, Sutcliffe, A. & Macaulay, L. (ed.), Cambridge University Press, 1989, pp. 443-460.

[Bertin83] Bertin, J.Semiology of graphics: diagrams, networks, maps . University of Wisconsin Press, Madison: 1983.

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