# Interface Usability
Derived from various usability literature, these 8 usability inspection criteria are meant to be used in critiques and evaluations of web applications.

### 💰 Affordance
Adaptation of an application features to a user’s changing needs

#### Requirements provision

- The set of functions offered by the system best caters to the needs and requirements of user

#### Choice availability

- Within a system state, a range of appropriate options are presented to perform an operation

### 🔦 Discoverability
Exchange of states and knowledge between an application and a user

#### State and feedback

- User is aware of their location, current state is visible, errors are prominent and actions are visible

#### Contextual help

- Material relating to the context of use is available for an object or its state and extended where needed

### 📖 Comprehension
Degree to which an application’s contents are clear to users

#### Accuracy and prominence

- Information conveyed by the system is accurate with certain components given emphasis

#### Perceptual clarity

- Objects are discernible, and grouped appropriately without appearing cluttered or misaligned

### 🚀 Efficiency

Cognitive load of an interface and its contents presented to a user

#### Visual metaphor

- System perpetuates a coherent conceptual model of function and organization from relevant metaphors

#### Cognitive simplicity

- Complex interactions are avoided while the steps to perform a function are minimized and without repetition

## References

- 30 Usability Principles, Connell & Hammond
- Designing Effective Speech Interfaces, Weinschenk and Barker
- Heuristics for User Interface Design, Nielsen
- 8 Steps to an Intuitive UI, McKay