Explanation
A subtask does not in itself achieve a goal from the user's point of view but is a necessary decision or action to reach the user's goals.

Explanation
Humancentred quality objectives
The goals that are to be achieved for the user of an interactive system when developing the interactive system.
Notes:
1. Human-centred quality objectives relate to one or more of the following components of human-centred quality: usability, accessibility, user experience and avoidance of harm from use.
Examples of human-centred quality objectives:
1. Travelers to the US must be able to pass through immigration twice as quickly as before (usability, efficiency).
2. Blind users must be able to recognise and understand the content of the website (accessibility).
3. Users must have a feeling of complete privacy when using the electronic voting booth (user experience).
4. When using a system for creating prescriptions, the user must not be able to prescribe drugs that are incompatible with each other (avoidance of harm from use)

Explanation
The purpose of "Design: produce design solutions to meet user requirements" is to convert user needs and user requirements into a working interactive system - that is, a design solution. Deliverables from the analysis of the context of use, such as user groups, as-is scenarios and personas are also used. The conversion considers dialogue principles, heuristics, style guides and design concepts like affordance and mental models as described in section 6.1. Design patterns are existing design solutions that have been shown to work for users and can therefore be reused in the designs of new interactive systems.
The approach is iterative as indicated by the following diagram: