Guideline 4. Clarify natural language usage.
Use markup that facilitates pronunciation or interpretation of abbreviated or foreign text.
When content developers mark up natural language changes in a document, speech synthesizers and braille devices can automatically switch to the new language, making the document more accessible to multilingual users. Content developers should identify the predominant natural language of a document’s content (through markup or HTTP headers). Content developers should also provide expansions of abbreviations and acronyms.
In addition to helping assistive technologies, natural language markup allows search engines to find key words and identify documents in a desired language. Natural language markup also improves readability of the Web for all people, including those with learning disabilities, cognitive disabilities, or people who are deaf.
When abbreviations and natural language changes are not identified, they may be indecipherable when machine-spoken or brailled.
4.1 Clearly identify changes in the natural language of a document’s text and any text equivalents (e.g., captions). [Priority 1]For example, in HTML use the “lang” attribute. In XML, use “xml:lang”.
4.2 Specify the expansion of each abbreviation or acronym in a document where it first occurs. [Priority 3]For example, in HTML, use the “title” attribute of the ABBR and ACRONYM elements. Providing the expansion in the main body of the document also helps document usability.
4.3 Identify the primary natural language of a document. [Priority 3]For example, in HTML set the “lang” attribute on the HTML element. In XML, use “xml:lang”. Server operators should configure servers to take advantage of HTTP content negotiation mechanisms ([RFC2068], section 14.13) so that clients can automatically retrieve documents of the preferred language.