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hierarchical task analysis

HTA or hierarchical task decomposition, HTD; breaking down the steps of a task (process) performed by a user, viewed at different levels of detail. Each step can be decomposed into lower-level sub-steps, thus forming a hierarchy of sub-tasks. The highest level of detail might be something like: open the word processor -> type your document -> print it -> quit. However, opening a word processor is not a one-step process. It might break down into something like: locate the word processing application icon -> click on the icon -> select Open from the File menu. A common level to break it down to is the “keystroke level”, where ever mouse movement, mouse click, and key click is identified. (see KLM, the keystroke level model).