18 1 Disability and Assistive Technology Systems

Figure 1.1. The HAAT model of an assistive technology system (after Cook and Hussey 2005)

3.Activity defines the procedure, operation or task that the human person wishes to achieve. The activity component is one of the more flexible terms within the model and depends on how the model is being used.

4.Assistive technology defines the external enabler used to overcome any contextual barriers or obstacles.

The HAAT model is presented in diagrammatic form in Figure 1.1.

International standards for assistive technology

International standards are relevant to modelling assistive technology. The current international standard which is often found in assistive technology databases and catalogues is ISO 9999: 2002 Technical Aids for Persons with Disabilities, Classification and Terminology. It is product and application orientated and divides assistive technology products into ten classes (with further divisions and subdivisions). The classes include aids for personal mobility, communications, information, signalling and recreation. Whilst the classification is comprehensive, it does not give a basis for understanding the structure of assistive technology systems. It is not a framework that can be used to analyse existing systems or synthesize new systems.

1.3.2 Modelling Human Activities

One aspect of assistive technology modelling that has received a certain, though again limited, amount of attention is that of modelling the human activities for which assistive technology support may be required. There are a number of different approaches depending on the desired end-use of the model and/or the perspective of the modeller. The section will discuss approaches derived from occupational therapy and the EU HEART project.

The occupational therapy classification uses the Uniform Terminology for Occupational Therapy (Dunn et al. 1994, 1995). It is based on three basic performance areas: daily living, work and productive activities, and play and leisure. Whilst these categories are useful for end-user assistive technology system assessment, there is a degree of ambiguity and overlap between them and, for engineering purposes, many of these activities need to be decomposed into a set of more fundamental task components. Table 1.1 shows two examples where there is a common subtask across occupational therapy activities.

The EU HEART project (HEART 1995) defines the four technical areas of communication, mobility, manipulation and orientation. Each area is further divided into activities and then sub-divided into categories of assistive technology devices. The activity categories for the four areas are as follows:

•Communications: interpersonal communications, reading/writing, computer access/user interfacing, telecommunications.

•Mobility: manual mobility, powered mobility, accessibility, private transportation, public transportation, orthoses, prosthetics, seating and positioning.

•Manipulation: environmental control, robotics, orthotics and prosthetics, recreation and sports.

•Orientation: orientation and navigation systems, cognition.

These categories can be further divided into different assistive devices. For instance, interpersonal communication includes hearing aids, optical aids, speech output: recorded and synthetic speech and low-tech devices, such as communication boards. Powered mobility includes powered wheelchairs, powered aids for lifting and transfer and robotic arms for wheelchairs.

There is therefore a need for a new classification scheme of the activity component to avoid ambiguity in task areas and to retain the link with what people actually do in their daily lives. The classification of human activities in the new comprehensive assistive technology model to be outlined in the next section was defined to meet the following specifications:

•To cover all (major) human activity areas whilst minimising overlap between different categories.

•To define activity areas which are sufficiently specific and are neither too wide nor too narrow. This appropriate breadth of categories results in definitions of