NICS - Guidelines for accessibility
Below is a simple illustration of a library. It shows 4 essential elements that are necessary to provide a good public library. All of these elements must be present in order to provide all borrowers with a positive library experience. If any are missing or defective then the library will not function appropriately.
Building - this could be anything from a portacabin to a listed building. Essentially it must provide the appropriate infrastructure to support the requirements of the library. There may be some constraints. For example, 'reasonable adjustments' may have to be made to a listed building in order to install an access ramp.
Access ramp - this is necessary to avoid excluding some potential borrowers with special needs from getting into and using the library (e.g. wheelchair users) and is a legal requirement (DDA 1995). Importantly, the ramp also assists others in using the library, e.g. parents with push chairs - benefits above and beyond its original purpose.
Bookshelves - the goal of most library users is to find and borrow a book. Good shelving with the books appropriately organised and cross-referenced is essential. If the books are randomly scattered or the shelves unreachable then no borrowers will be able to use the library effectively (even though all can get access to the library itself).
Librarian - the 'public' face of the library. An enthusiastic and helpful librarian assists new borrowers to register and find their way around, and welcomes repeat borrowers - generally creating a beneficial and pleasurable experience for all users. This results in a library with an enhanced reputation, and that will be significantly better utilised. An unhelpful, prejudiced librarian will deter all potential users but particularly those that they discriminate against.
The 4 elements of the library are analogous to the required elements necessary to create an effective, usable, universal web site:
Technical accessibility (access ramp) - this refers to the underlying code (HTML etc.) of the pages of the site that are presented. Bad code will prevent some users (e.g. screen reader users) from being able to access the information presented. Technical accessibility represents adherence to accessibility guidelines (e.g. WAI guidelines - see later) but merely conforming to the guidelines alone is not enough to ensure that all people can actually use the site.
Analogy: Just getting into the library does not mean that a book can actually be borrowed - it requires a good librarian and appropriate and 'all-user friendly' shelving.
The technical accessibility of sites needs to be addressed. But this alone is not enough. The other aspects - namely usability and organisational constraints - must also be implemented.
Usability: Interface (librarian) and information architecture (bookshelves) - A site with very poor usability will be unusable by everyone, with or without special needs. However poor usability tends to affect those with special needs more severely - such that they are hindered or prevented completely from performing tasks that those without special needs can complete comfortably. The problems can be caused by information architecture issues (poor labeling, poor organisation), or other aspects of the interface (poor navigation, lack of appropriate assistance provided, inappropriate tone, etc.).
Analogy: A library with a ramp would be effectively unusable to someone in a wheelchair if the librarian was unhelpful and discriminatory, and/or some of the shelves were too high.
The 'use in practice' for a full range of potential users needs to be tested (including people with disabilities). This will lead to enhanced usability for everyone (the usability bonus).
Organisational/Implementation constraints (building) - Even with knowledge of the issues and a positive attitude towards accessibility, there may still be practical considerations and constraints that restrict the ability of organisations to provide an accessible web site.
Analogy: A listed building will probably have different issues and constraints for erecting an access ramp as compared to a new building. Such issues might change the definition of 'reasonable adjustments'.
Organisational/implementation constraints are factors that affect an organisations ability and readiness to implement accessibility. For example awareness, attitude, technical issues, resource limitations. Practical and pragmatic solutions must be sought.
Only Technical accessibility + usability = True accessibility
You need the ramp, good shelves, and a happy librarian.