INFO2222 · Computing 2 Usability and Security
Design and Prototyping
Week 3 turns design ideas into testable artefacts: personas and scenarios bring requirements to life, and prototypes let stakeholders interact with a design before it is built. Justifying a prototyping choice — low- vs high-fidelity, horizontal vs vertical — is exactly the kind of apply-and-select item the final exam asks, and the ideas feed directly into the group project's design work.
What this chapter covers
- 01Personas (fictional but realistic target users) and scenarios (informal narratives in the user's own vocabulary)
- 02Two aspects of design: conceptual design (the idea, metaphors, interaction types) vs concrete/physical design (the details)
- 03Interface metaphors (e.g. the desktop) — advantages (easier to learn) and disadvantages (constrain the design)
- 04Interaction styles: instructing, conversing, manipulating, exploring, responding — chosen per task
- 05What a prototype is and why prototype: early feedback, team communication, feasibility, cheap change, reflection
- 06Fidelity: low-fidelity (paper, Wizard-of-Oz — quick, cheap, changeable) vs high-fidelity (near-final, interactive, slower to change)
- 07Scope: horizontal prototype (wide, shallow) vs vertical prototype (narrow, deep); usually combine both
- 08The revision trap: low-fidelity prototypes CAN still gather user feedback (a common false statement)
Choose a prototype's fidelity and scope for an early design
- +1(a) For quick reactions to three competing layouts, use a low-fidelity, horizontal prototype (e.g. paper sketches or wireframes): it is cheap and fast to change, and horizontal scope shows a wide range of screens at shallow detail so students can react to the overall structure.
- +1Justify the low-fidelity choice: at an early stage with many open questions you want to explore alternatives and revise them cheaply; fidelity should rise only as open questions shrink (lo-fi → hi-fi).
- +1(b) For proving the timetable-import feature works end to end, use a vertical prototype at higher fidelity: vertical scope means deep detail on a few functions, and higher fidelity is warranted because you are now testing technical feasibility of one specific path.
- +1(c) The teammate is incorrect. Low-fidelity prototypes CAN gather user feedback — that is a main reason to build them. Waiting for a high-fidelity build wastes the cheap, early feedback that catches the biggest problems.
Key terms
- Persona
- A fictional but realistic character representing a target user group, with a name, role, demographics, goals, environment and a representative quote. Built from user research and refined to about three to five; kept realistic (no humour, no excess personal detail).
- Scenario
- An informal narrative (Carroll) describing users' activities and tasks in their own vocabulary. It helps designers spot stakeholders, artefacts, what is central, and the constraints and irritations of a task.
- Conceptual vs concrete design
- Conceptual design is the idea of the product — what users can do and the metaphors and interaction types needed to understand it. Concrete (physical) design is the detail — widgets, colours, icons, layout — subject to practical constraints. The two are intertwined and iterated together.
- Prototype fidelity
- How close a prototype is to the final product. Low-fidelity (paper, cardboard, Wizard-of-Oz) is quick, cheap and easily changed; high-fidelity uses near-final materials, is interactive and detailed but slower to change, and risks people thinking it is finished.
- Horizontal vs vertical prototype
- Horizontal = a wide range of functions at shallow detail (good for overall structure). Vertical = deep detail on a few functions (good for testing one path or feasibility). A typical approach combines both.
- Wizard of Oz
- A low-fidelity technique where the user believes they interact with a computer, but a hidden human 'wizard' interprets input and generates responses per an algorithm. Good for simulating complex or futuristic functionality early.
Design and Prototyping FAQ
When should I use a low-fidelity versus a high-fidelity prototype?
Use low-fidelity early, when many questions are open: paper sketches and wireframes are cheap and fast to change, so you can explore and discard alternatives quickly and still get real user feedback. Move to high-fidelity as the open questions shrink and you need to test interaction detail or technical feasibility. High-fidelity is more resource-intensive and slower to modify, and there is a risk that users and management treat it as finished and are reluctant to criticise it.
What is the difference between horizontal and vertical prototypes?
They describe scope, not polish. A horizontal prototype covers a wide range of functions with little depth — good for evaluating the overall structure and navigation. A vertical prototype implements a few functions in full depth — good for testing one important path end to end or proving feasibility. Real projects usually combine a broad overview with a couple of deep paths.
Is it true that low-fidelity prototypes can't get user feedback?
No — that is a classic false statement the revision material calls out. Gathering early user feedback is one of the main reasons to build a low-fidelity prototype. Read exam statements like this carefully, because the multiple-answer format often plants a plausible-sounding negative.
Can AI help me with design and prototyping in INFO2222?
Yes, as a study aid. Sia can help you draft or critique a persona, tell a persona from a scenario from a user story, and reason about which fidelity and scope suits a design stage and why. Use it to rehearse the concepts and sharpen your project's design justification; it does not produce your graded project deliverables, and the University of Sydney academic-integrity policy applies.
Exam move
Build two quick reference cards. Card one: the fidelity axis (low = paper/Wizard-of-Oz, cheap and changeable; high = near-final, interactive, slow) and the scope axis (horizontal = wide/shallow, vertical = narrow/deep), because exam items ask you to pick and justify a combination for a given stage. Card two: personas vs scenarios vs user stories, so you can tell them apart, plus the five interaction styles and the pros/cons of interface metaphors. Rehearse the rule 'fidelity rises as open questions close', and memorise the false-statement trap that low-fidelity prototypes cannot get feedback. Apply all of this to your own group-project design so the revision doubles as project work. Confirm assessment weights and deadlines on Canvas.
Working through Design and Prototyping in INFO2222? Sia is AskSia’s AI Computer Science tutor — ask any INFO2222 Design and Prototyping question and get a clear, step-by-step explanation grounded in how INFO2222 is taught and assessed. Read this chapter free, then take your hardest questions to Sia.
