Humans are typically equipped with five senses and the capability for making a broad variety of movements that can modify a person's appearance, apply forces to objects in the surrounding environment, or generate sounds and speech. Failure, degradation, or overloading of any of our senses or physical capabilities reduces our ability to function in the world. Accessibility engineering seeks to provide technologies that augment or, when necessary, replace individual capabilities. While there is no end to the number of ways in which individuals can be impacted by the different combinations of disability type and severity, this is only half of the equation.
The world is similarly complex, with untold combinations of devices and processes with which humans must interact. Bringing these two halves of the equation together yields an almost incomprehensible range of unique combinations of user and equipment requirements. In IT terminology, we have a "many-to-many" problem. For example, if we have five disabilities and five target systems to be accessed, we must provide twenty-five unique solutions (i.e. the product of user interfaces and machine interfaces) to cover every possible combination. A better solution is to break the problem into two parts: use a many to one solution to provide interfaces to the disabled users, and a one to many solution to provide interfaces to the target devices. In this case we need only 10 solutions (i.e. the sum of five user interfaces and five machine interfaces) to cover all combinations.
Traditional accessibility solutions are based on the many-to-many strategy. A particular IT device is modified to make it uniquely accessible to a particular individual with a disability. A different one-off solution is required for every person. Such one-off solutions are time consuming and costly to design and implement and, in their own way, introduce new problems such as limiting the user to a specific item of equipment at a fixed location. The continual evolution of IT equipment and software rapidly obsoletes these personalized accessibility solutions.
