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Contributions to this document are very welcome, however significant changes should be first discussed on the dc-accessibility mailing list. To join or leave the dc-accessibility mailing list, please visit http://www.jiscmail.ac.uk/lists/dc-accessibility.html.

AccessForAll: an Accessibility Framework

Introduction

This document explains the AccessForAll accessibility framework. The intended audience of this document is anyone interested in accessibility and standards, especially those from the metadata community. A small proficiency in software design is assumed from the reader (for this document uses UML in some of its explanations), however the hope is that the concepts are explained clearly enough to be understood by readers of any technical skill-level.

What is AccessForAll

AccessForAll is a framework designed to define and describe resource accessibility. Its goal is to provide a means whereby resources are matched to the accessibility preferences expressed within an individual preference set. The framework is divided into the following concepts, which, when used in conjunction, make possible the matching of resources to preference sets and the description of resource accessibility:

These concepts and their interaction will be discussed further in this document, alongside the presentation of the AccessForAll abstract model.

History

The concepts behind the AccessForAll framework were originally developed by the IMS Accessibility Working Group1. The working group defined two specifications: the IMS Accessibility for Learner Information Package (AccLIP) and the IMS AccessForAll Meta-data [sp] Specification (AccMD). Together they defined what is currently the AccessForAll framework in an applied, XML-specific way. This document hopes to explain the main concepts behind the AccLIP and AccMD, i.e. the AccessForAll framework, in an abstract way.

AccessForAll Abstract Model

Introduction

This section specifies an abstract model for the AccessForAll framework. The primary purpose of this section is to provide a reference model against which particular metadata encodings can be written.

AccessForAll abstract model

The abstract model of the preference sets defined in the AccessForAll framework is as follows:

The abstract model of the resources defined in the AccessForAll framework is as follows:

The AccessForAll abstract model for resources and recods is represented as a UML class diagram in the following illustration:

http://accsig.atrc.utoronto.ca/AccessForAll/AccessForAll-AbstractModel.png

Readers not familiar with UML class diagrams should note that lines ending in a block-arrow should be read as 'is' or 'is a' (for example, 'a required access mode is an access mode ') and that lines starting with a block-diamond should be read as 'contains a' or 'has a' (for example, 'an adaptation property / value pair has a value and a property'). Other relationships are labeled appropriately3.

http://uml.sourceforge.net

Access mode

An access mode is the human sense or medium though which a user receives the output of a resource. The mode refers to either the perceptual system, or the cognitive faculty engaged by the user. An access mode is defined either as a sense, to reference a perceptual system, or as a medium to connect with a cognitive ability. Some examples will clarify:

Describing a resource's access mode as “visual” implies that a user will use their visual system to process it. Pictorial and video resources are examples of such resources.

Describing a resource's access mode as “textual” implies that a user will rely on their ability to read in order to understand the resource's content4.

Alternative resource

An alternative resource is the same intellectual content of the referenced resource, but presented in another access mode.

Adaptation preference and property

An adaptation preference states how a user desires to access a resource. In effect, it defines how a resource should be adapted in order to provide adequate means of access to a user. An adaptation property is a statement describing characteristics of the resource that affect how it can be sensed, understood, or interacted with by users or agents5. The two share a reflexive relationship in that an adaptation property matches an adaptation preference.

Conforms to

A reference to an established standard to which the resource conforms6.

Putting it all together

Preference Set

A user is able to state his/her required and prohibited access modes. In this way a user can state what he/she wants and what he/she does not want for an access mode. In addition to this for each required, prohibited, or combination of required and prohibited access modes, a user is able to state his/her adaptation preferences. Adaptation preferences may qualify the required and prohibited access modes with information about the adaptation characteristics of the resources the user wishes to interact with, however they may also stand alone.

Resource

A resource declares its access mode(s). A resource may be an alternative to another resource and another resource may be an alternative to it. In addition to its access mode(s), a resource states its adaptation properties. A resource may conform to a number of standards.

Matching resources to preference sets

The goal of the AccessForAll framework is to match resources to preference sets. The following is a list of guidelines for matching resources to preference sets:


Appendix A Relationship with Web Content Accessibility Guidelines (WCAG)

The Web Content Accessibility Guidelines (WCAG) are a set of principles and guidelines that define and explain the "requirements for making Web-based information and applications accessible to a wide range of people with disabilities7." The WCAG does not define new technologies, but rather techniques that can be applied to any type of Web content. The AccessForAll framework defines a different approach to resource accessibility, however one that complements the WCAG: The AccessForAll Framework states (via metadata on resources) the accessibility properties that are recommended by the WCAG. This enables the AccessForAll Framework a means whereby resources can be matched to the accessibility preferences expressed within an individual preference set.

Appendix B Editors

Appendix C Contributors

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