上海时时乐时时彩:How WCAG 2.0 Differs from WCAG 1.0
上海时时乐上 www.tf5x.com.cn This page describes how WCAG 2.0 is different from WCAG 1.0. For background, an introduction to WCAG, and links to additional information, see Web Content Accessibility Guidelines (WCAG) Overview.
WCAG 2.0 applies more broadly to different types of Web technologies and to more advanced technologies. It is designed to apply as technologies develop in the future.
The WCAG 2.0 requirements are more precisely testable with automated testing and human evaluation. This allows WCAG 2.0 to be more easily used where specific requirements and conformance testing are necessary, such as in design specifications, purchasing, regulation, and contractual agreements.
WCAG 2.0 was developed in coordination with international efforts to harmonize on a single standard for Web content.
Along with WCAG 2.0 there is extensive support material with guidance and examples, making it easier to understand and use.
See the Benefits of WCAG 2.0 presentation.
WCAG 1.0 is organized around guidelines that have checkpoints, which are priority 1, 2, or 3. The basis for determining conformance to the WCAG 1.0 are the checkpoints.
WCAG 2.0 is organized around four design principles of Web accessibility. Each principle has guidelines, and each guideline has testable success criteria at level A, AA, or AAA . The basis for determining conformance to the WCAG 2.0 are the success criteria.
The WCAG 2.0 Layers of Guidance section of WCAG 2.0 provides more information on the principles and success criteria.
In WCAG 2.0, a single issue can be covered by more than one success criteria at difference levels. For example, color contrast is covered by two success criteria:
- Level AA: The visual presentation of text and images of text has a contrast ratio of at least 4.5:1...
- Level AAA: The visual presentation of text and images of text has a contrast ratio of at least 7:1...
In WCAG 1.0, brief descriptions are included in the main WCAG 1.0 document under each guideline. Most of the examples are for HTML content.
The WCAG 2.0 standard has technology-independent guidelines and success criteria without the additional descriptions. The descriptions are in the supporting documents Understanding WCAG 2.0 and Techniques for WCAG 2.0. These provide extensive guidance, including the intent of the guideline or success criterion; how it helps people with different disabilities, browser and assistive technology support notes, examples, and resources, such as tools to check color contrast. Techniques provide general and technology-specific examples, including for HTML/XHTML, CSS, scripting, multimedia, and WAI-ARIA. There are also common failures that show what to avoid.
WCAG 1.0 has a basic checklist. WCAG 2.0 has a customizable quick reference that you can use to create a short high-level checklist or long detailed checklists: How to Meet WCAG 2.0: A customizable quick reference. It is essentially the WCAG 2.0 checklist.
See The WCAG 2.0 Documents for details on how the WCAG 2.0 documents relate and how they are linked.
Comparison of WCAG 1.0 Checkpoints to WCAG 2.0 lists the new requirements in WCAG 2.0, and shows how each WCAG 1.0 checkpoint relates to WCAG 2.0. The Comparison is available in two versions:
- Comparison organized by WCAG 1.0 checkpoint numerical order
- Comparison with WCAG 1.0 checkpoints grouped by priority
Most Web sites that conform to WCAG 1.0 should not require significant changes in order to conform to WCAG 2.0, and some may not need any changes. The fundamental issues of Web accessibility are the same, though there are some differences in the organization and requirements between WCAG 1.0 and WCAG 2.0.
To help you move to WCAG 2.0, WAI is developing:
- How to Update Your Web Site from WCAG 1.0 to WCAG 2.0
- Guidance on transitioning Web Accessibility Policies to WCAG 2.0
WCAG 2.0 is backwards compatible so that a site can meet both WCAG 1.0 and WCAG 2.0.