Task analysis

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Introduction and definitions

Task analysis is a frequent design and research problem and method. For now, this entry shall focus on task analysis in design and usability. - 23:17, 26 April 2011 (CEST)

Definitions for user task analysis

According to Task Analysis (retrieved 17:09, 26 April 2011 (CEST)) “Task analysis involves learning about your users' goals, what they want to do on your Web site and how they work. It can also mean learning about specific task users must do to meet those goals and what steps they take to accomplish those tasks. A task analysis complements a user analysis. [...] Tasks analysis allows you to discover what tasks your Web site must support and to determine the appropriate content scope. It also helps you to decide what applications your Web site should include. It can assist you in refining or re-defining the navigation or search to better support users' goals or to build pages and applications that match users' goals, tasks, and steps.”. Usability.net provides a similar definition.

According to NASA's Usability toolkit, retrieved 17:09, 26 April 2011 (CEST), “Task analysis defines what a user is required to do in terms of actions and/or cognitive processes to achieve a task. A detailed task analysis can be conducted to understand a system and the information flow within it. These information flows are important to the maintenance of the system. Failure to allocate sufficient resources to this activity increases the potential for costly problems arising in later phases of development. Task analysis makes it possible to design and allocate tasks appropriately within the new system. Once the tasks are defined, the functionality required to support the tasks can be accurately specified.”

“Task Analysis is the step of usability analysis in which goals and the tasks to achieve them are explicitly defined, in order to provide a more detailed, critical understanding of the steps and the relationship between them. By explicitly defining and then evaluating, in terms of overall strategy and action oriented tactics, a goal may be more efficiently and better implemented. Often, by trying to explicitly define a goal, the methods become clear. Then, the tasks which the user goes through in order to achieve the goal can be actively analyzed, critiqued and reworked, increasing efficiency and usability.” Ian Seymour, Student project, Geogia Tech, CS 6751, 1997


According to Crystal and Ellington (2004), there exists are larger variety of task analysis approaches and techniques.

For the moment, we just present the most popular variety, i.e. hierarchical task analysis (HTA) (Annet & Duncan, 1967, Shepperd, 2001).

Hierarchical task analysis

“The underlying technique, hierarchical decomposition (Annett, Duncan, Stammers and Gray, 1971), analyzes and represents the behavioral aspects of complex tasks such as planning, diagnosis and decision making (Annett and Stanton, 2001). HTA breaks tasks into subtasks and operations or actions. These task components are then graphically represented using a structure chart. HTA entails identifying tasks, categorizing them, identifying the subtasks, and checking the overall accuracy of the model. [...] HTA is useful for interface designers because it provides a model for task execution, enabling designers to envision the goals, tasks, subtasks, operations, and plans essential to users’ activities. HTA is useful for decomposing complex tasks, but has a narrow view of the task, and normally is used in conjunction with other methods of task analysis to increase its effectiveness.” Crystal and Ellington (2004:p)

According to Usability.net, retrieved 17:09, 26 April 2011 (CEST), a typical hierarchical task analysis consists first in breaking down a high-level task “into constituent subtasks and operations. his will show an overall structure of the main user tasks. At a lower level it may be desirable to show the task flows, decision processes and even screen layouts (see task flow analysis, below)”. Such a task decompositions can be carried out using the following stages:

  1. Identify the task to be analysed.
  2. Break this down into between 4 and 8 subtasks. These subtasks should be specified in terms of objectives and, between them, should cover the whole area of interest.
  3. Draw the subtasks as a layered diagram ensuring that it is complete.
  4. Decide upon the level of detail into which to decompose. Making a conscious decision at this stage will ensure that all the subtask decompositions are treated consistently. It may be decided that the decomposition should continue until flows are more easily represented as a task flow diagram.
  5. Continue the decomposition process, ensuring that the decompositions and numbering are consistent. It is usually helpful to produce a written account as well as the decomposition diagram.
  6. Present the analysis to someone else who has not been involved in the decomposition but who knows the tasks well enough to check for consistency.

Once tasks are analyzed they also can be represented as task flow diagrams also called task maps. “Task flow analysis will document the details of specific tasks. It can include details of interactions between the user and the current system, or other individuals, and any problems related to them. Copies of screens from the current system may also be taken to provide details of interactive tasks. Task flows will not only show the specific details of current work processes but may also highlight areas where task processes are poorly understood, are carried out differently by different staff, or are inconsistent with the higher level task structure.” (UsabilityNet.org).

One could use formal workflow languages such as UML activity diagrams or BPMN 1.2 for such diagrams.


  • TaskArchitect is a (hierarchical) task analysis tool. A free version allows to define 20 tasks and 10 properties. Standard and Pro versions are $400, $1250.


Short introductions
Web sites or links pages


  • Annett, J. and Duncan, K. (1967). Task Analysis and Training Design. Occupational Psychology 41, 211-221.
  • Annett, J., and Stanton, N., eds. (2000). Task analysis. London: Taylor & Francis.
  • Crandall, B., Klein, G., Hoffman, R. R. (2006). Working Minds: A Practitioner's Guide to Cognitive Task Analysis. MIT Press, ISBN 9780262532815.
  • Shepherd, A. 1989, Analysis and training in information technology tasks, in Diaper, D (Ed), Task Analysis for Human-Computer Interaction, Chichester, Ellis Horwood.
  • Shepherd, A. (2001). Hierarchical task analysis. New York: Taylor & Francis.