In the last unit we looked at user models and modelling. Users usually have goals and carry out tasks to achieve those goals (interacting with a computer system as necessary). In this unit we will look at ways of modelling tasks. There are different types of task model. All of the techniques concern goal-oriented things that people do but some focus on the actions carried out to achieve a goal; some on the knowledge required to carry out a task; and, others on the relationships between the objects involved in the task. This unit will review three major types of model (Hierarchical Task Analysis, Knowledge Based Analysis and Entity Relationship modelling). You will see how they are employed in systems development. We will focus on HTA and you will learn how to produce this sort of analysis and how the results can be used.