Principles1 for the design of interactive technology

A.  Ontological Heuristics

1.  Simplicity
2.  Visibility
3.  Consistency
    i. internal
   ii. external
4.  Stability 		  a.  of objects.
b.  of actions.
c.  of properties.
d.  of relationships.
e.  of constraints.
f.  of system status.

B.  Interaction

1.  Objects
a.  Form indicates function.
b.  Can be directly manipulated.
c.  Flexible, tailorable.
2.  Actions
a.  Efficient, not repetitive.
b.  Reversible, undoable.
c.  Accessible via shortcuts.
d.  Not required when unnecessary.
e.  User always in control.
3.  Navigation
a.  Obvious, pervasive.
b.  Reversible.
c.  Exits clearly marked.
d.  Landmarks used; user does not get lost.
e.  "Home" provided and easily returned to.
f.  "Dead ends" avoided where only action is to exit.
4.  Data
a.  Persistent.
b.  Expected types and formats clear.
c.  Appropriate defaults set and restorable.
d.  Recommended values identified.
e.  Units and ranges clear and intuitive.
5.  Feedback
a.  Present for all actions.
b.  Shown when system status changes.
c.  Continual for lengthy operations.
6.  Messages
a.  Helpful and appropriate.
b.  Intrusive only when necessary.
c.  Timely – presented when users can act on them.
7.  Errors
a.  Users protected from making them.
b.  Offer remedies and next steps.
c.  Not damaging; recoverable.
d.  Avoid blaming the user.
8.  Language
a.  Accurate and concise.
b.  Avoids jargon and "programmerisms."
c.  Employs consistent terms throughout.
d.  Accompanied by images where appropriate.
e.  Uses proper terminology and capitalization.
f.  Expresses user’s perspective, not system’s.
9.  Help
a.  Available everywhere.
b.  Context-specific.
c.  Gives step-by-step instructions.
d.  Searchable.

C.  Cognitive and Perceptual

1.  Affordances
a.  Not hidden.
b.  Not false.
c.  Feedback used to aid.
2.  Attention
a.  Drawn by emphasis.
b.  Focus clear, not divided.
c.  Limits not exceeded.
d.  Parallel channels used.
3.  Human memory
a.  Recognition used rather than recall.
b.  Special cases and exceptions minimized.
c.  Never more than 7 ± 2 items required for recall.
d.  Burden carried by computer whenever possible.
4.  Auditory channel
a.  Not used in isolation.
b.  Usually should accompany errors.
5.  Visual layout
a.  Good use of screen real-estate.
b.  Good visual segmentation.
c.  Important information prominent.
d.  Moderate to high information density.
e.  Aesthetic.
6.  Color
a.  Minimalist use.
b.  Avoids arbitrary assignment.
c.  Red used in errors, avoided elsewhere.
d.  Foreground distinguishable from background.
e.  Usable in black and white.

D.  Conceptual Model

1.  System motifs
a.  Are employed throughout.
b.  Match user thinking.
2.  Information architecture
a.  Structure supports user goal structure.
b.  Structure accurately reflects relationships.
c.  Information available when and where needed.
d.  Sequences mimic user decision sequences.
3.  Modes
a.  Avoided when possible.
b.  Obvious when in effect.
c.  Active over passive.
4.  Natural mappings
a.  From controls to objects (input).
b.  From displays to objects (output).
5.  Metaphors
a.  Accurately communicate mental model.
b.  Deep enough to be of value.
c.  Beyond "mechanical age."
d.  Not broken, rarely mixed.
6.  Clear path
a.  Program opens at conceptual beginning.
b.  Most likely actions are most accessible.
c.  Interface encourages exploration.
d.  Complexity layered and hidden.

1 Heuristics and guidelines adapted from various sources, including Nielsen and Mack Usability Inspection Methods (1994), Nielsen Usability Engineering (1994), Norman The Design of Everyday Things (1990), and many others. This categorized medium-length list is meant to be more expressive than the high-level list of ten heuristics by Nielsen, yet more usable as a checklist than Tog’s informative but lengthy prose.