Analyzes tasks

The goal of the analysis of the tasks is to highlight and to describe the tasks to be carried out to achieve a work.

A very fine analysis of the tasks can be also used to predict or explain the performances of a user in a given environment.

Terminology

An objective is a state of a system which an agent (human) wishes to reach (to write a letter, to obtain a diploma, etc)

It is possible various (methods, tools, etc) to achieve the goal.
the selection of the means determines the task to undertake.
an objective must have a certain stability in time.

A task is an activity (regarded as) necessary, or used to achieve a goal by using a given means. A task is in general decomposable in sub-tasks, up to the level of the actions.

A action (or tries elementary or links task ) is a task not implying a resolution of problem or of structure of control (alternatives, repetition,…). It is generally focused on objects.

One can say that the analysis of the tasks consists in connecting objective, tasks and actions. It is a question of including/understanding the objectives of the users and of including/understanding how they pass from the objectives to the tasks then to the actions. It is also important to know what occurs in the event of problem.

Models of tasks

The goal of the analysis of the tasks is to produce a list of the tasks and a job analysis and their interactions.

Many models (formalisms) were developed for that (DIANE+H, MAD, K-MAD, CTT, AWG, GOMS, UAN, etc). These models in general make it possible to express the following characteristics:

decomposition of a task in sub-tasks (with possibly a typology of the tasks)
of the relations of temporal scheduling of the sub-tasks (sequence, alternative, parallelism, etc)
which are the goals and under-goals and the tasks which make it possible to reach them
which are the objects used to achieve a task or an action

Applications

Design of a man-machine interface

In the field of the man-machine interfaces (IHM), this analysis is a crucial step of the design and evaluation of the interfaces. Indeed, each function of the interface of an application (each interaction) must contribute to the realization of a task or part of a task of the user. The analysis of the tasks thus fixes a framework and objectives at the originator of interfaces.

A very fine analysis of the tasks can be also used to predict or explain the performances of a user with a given interface.

If the purpose of the models of tasks are primarily to help to conceive the man-machine interfaces, there exist models designed to carry out a cognitive analysis of the tasks, in the idea to calculate in advance or to explain the performances of the users. Most known of these models is GOMS (goal, operator, method selection). To predict the performance of a user, GOMS takes into account not only the execution time of the elementary operations (striking of a key, movement of the mouse, etc) but also the cognitive effort, and thus the time necessary with the selection of the methods (tasks): will I use a menu, a short cut keyboard?

References

D. Diaper, NR. Stanton (Eds) The Handbook off Task Analysis for Human-Computer Interaction.
J. Preece and Al Human-Computer Interaction, Addison-Wesley, 1994.
S. Greenberg. Task-Centered System Design. U. off Calgary.

Race slides.

Random links: