From HTML WG Wiki
Issue 30 longdesc Change Proposal
The following is a Change Proposal for ISSUE 30 when it is reopened.
Editor: Laura Carlson
Date: January 31, 2011, last updated February 1, 2011.
Please address feedback to the HTML Working Group mailing list (firstname.lastname@example.org).
Instate the longdesc attribute from HTML 4 into HTML5 as an allowed attribute on images.
Uses cases have been identified that specifically require longdesc.
Formal Use Cases
For formal use cases requiring longdesc, please visit Long Description Research: Use Cases.
Primary Use Case Overview
Longdesc affords authors the native capability to provide information that is essential for blind and visually impaired users but would be redundant for sighted users and unacceptable to visual designers' aesthetics.
It is an accommodation mechanism for people who are blind or have a visual impairment and use a screen reader. It is a tool to supply programmatically determinable descriptions of images such as data visualization (i.e. charts and graphs), diagrams, cartoons, logos drawings, illustrations, maps, photographs, etcetera when:
- An image's content is visually apparent and typically redundant to a sighted person, and/or
- It is unacceptable to a marketing department or web author to use another technique due to aesthetic considerations. Many artists, designers and marketers do not want their visual designs changed/ruined with visible link text. (Longdesc is naively free from a visual encumbrance.), and/or
- The image also serves as a link. With longdesc it is programmatically possible to separate the activation of the longdesc for exposure from the UA's universal link activation action (which is usually activated with the ENTER key, the SpaceBar, or by mouse click), so that the linked image retains the expected behavior in response to user interaction while a discrete mechanism is used to retrieve the long description.
The cartoonist Kyle Weems (aka CSS Squirrel) has explained:
@Nick - With the exception of this most recent comic, all the comics are made for sighted users and navigable via the previous/next links below the comic. Those links are targetable by the sort of technology a physically-disabled person would use to navigate most links.
The issue at hand was directed at a piece of technology made for non-sighted users, however, so this comic provided an exception to deal with that specific experience.
@Mattur - I have no qualms with other people using hyperlinks where they desire to provide alternate text. However, as a designer, I object to being told I must use those links myself. As you've pointed out on Twitter, the current design of the comic page would certainly support a hyperlink wrapping around the comic. However, my upcoming design already has functionality mapped to clicking the comic, and won't have space for a large "transcript here" hyperlink sitting around in plain sight (which would be distracting for the 99% of my users that are sighted). In that scenario, longdesc can and does serve my needs.
Also, are we going to pretend that using longdesc is difficult? Yes, people may use it wrong without some correction, but simply saying "Hey, put a URL there," is not complex at all, and most of longdesc's non-use is a lack of awareness or caring (most non-longdesc websites simply don't offer alt text at all.)"
Other Use Cases
The content in a longdesc's target explains what is visually evident. This is similar to an audio description of a video being redundant to people who can see. Audio descriptions describe items that take place visually which are needed for complete understanding to people who can't see. Sighted users don't typically need them. The same is true of longdesc.
However, the following sighted people may be aided by access to a longdesc:
- Users who have a cognitive impairment that makes it difficult or impossible to read, and use a screen reader.
- Users who have a visual impairment, but who do not use assistive technology.
- Users who turn off images to decrease bandwidth use in order to lower their Internet usage fees.
- Users who have a cognitive impairment, but who do not use assistive technology, who need the long description in order to process the image properly/in the intended order; such users may also benefit from the structured content of a verbose descriptor (for example, the use of an ordered list).
- However, the majority of people with cognitive impairments would be aided more by a simplified step-by-step visual. Text would be additional clutter and cause confusion as it can create difficulties for users with cognitive impairments. Appropriate graphics can be used to help reduce cognitive load and enhance understanding Cite: Jiwnani, K. "Designing for Users with Cognitive Disabilities", (2001).
- Authors for ease of authoring and maintenance purposes.
Access to the content of longdesc attribute for the sighted should be similar to television closed captions. Closed captions are encoded or invisible to the sighted by default and must be decoded or made visible. There is a reason that closed captions (as opposed to open captions) are the default on televisions. Sighted people rarely require them. To them, they are visual noise. Clutter. Redundant. But if a sighted person wants to enable closed captions they can do so via a user preference built into the system menu. It is a user choice. Televisions do not have a default on-screen visual indicator. There is no forced visual encumbrance. This is by design.
The 80/20 rule is not applicable for longdesc. Usage is not and will never be widespread because:
- People With Disabilities are a minority.
- Images that need longdesc are a minority.
However, longdesc has been used in that minority. The longdesc attribute is in current use on a multitude of company, organizational, governmental, educational, and personal sites throughout the world, including but not limited to
- New Zealand
- South Korea
- United Kingdom
- United States
Visit Research: longdesc for examples in the wild.
Numerous sites do not have longdesc visual indicators. Some go to great lengths to hide a longdesc visual indicator via invisible D-link or invisible
Modern screen readers have good support of the longdesc attribute. They typically announce the presence of a long description when available, and provide users with the option of reading it by executing a specified keystroke. But in an effort to mitigate damages of user agents that do not yet have a long description feature built directly into them, some sites provide a separate redundant link or a D-link to the long description. This link does not programmatically tie the image to the description. With proper implementation in browsers these could all be solely longdesc.
Failure by some browser vendors to fully implement a feature is not in itself sufficient justification for getting obsolete it. However, longdesc has been implemented.
- Opera (native support) -- exposition of the longdesc is exposed by a right click on the image for which the longdesc has been defined) -- it has been requested that the
IMGfor which longdesc has been defined, be included in the tab order so that navigation to and exposition of longdesc is device independent
- iCab (native support for longdesc
- FireFox - partial native support via the image context menu, which displays the URI of the longdesc attribute
- Internet Explorer when used together with assistive technology like JAWS makes longdesc accessible to the user
- Longdesc Linker for Internet Explorer 6 -- Browser Helper Object (BHO) which adds a "Long Description" item to the context menu that IE uses for images
- SeaMonkey -- discloses longdesc URI via <right-click>/<properties>/Description
- Connexions Markup Language (CNXML)
- Cute Editor
- easyALBUM -- screen reader friendly. The "slideshow" uses 3 attributes:
- Expression Studio
- Expression Web
- IBM Lotus Domino Designer 8.5
- iGraph-Lite can "generate rich descriptions alongside graphs through the longdesc tag", Evaluatinga tool for improving accessibility to complex visual objects (PDF document) Ferres, L., Lindgaard, G.,Sumegi, L. 2010
- Juicy Studio's Image Analyser
- LongDesc Page Generator
- Quail PHP Accessibility Library
- RadEditor for ASP.NET AJAX
- SiteVision.se CMS
- YAG Image Gallery
- WAVE -- detects whether the longdesc value is structured as a proper URL. This feature was implemented January 2009. Jared Smith from WebAIM expects in a new release of WAVE to have implemented longdesc URL checking that looks for even more of the common errors.
- WordPress longdesc Plugin
- JAWS (Version 4.01 and up)
- LookOUT in combination with WebbIE
- Sense Reader Professional Edition v188.8.131.52 (Korean)
Other Tools Supporting Longdesc
Further longdesc Advantages
- Provides authors the native capability to provide information that is essential for blind users but would be redundant for sighted users and unacceptable to visual designers' aesthetics.
- Does not force a visual encumbrance or default visual indicator on sighted users.
- Allows screen reader users freedom of choice. The description is not forced upon them whether they want it or not. They can interact with it at their own will. With other solutions like aria-describedby this is not possible.
- Allows structured content in it's target.
- Programmatically ties the description to image. A long description needs to be programmatically determinable. This relates to the information in web content. If technologies that are accessibility supported are used properly, then assistive technologies and user agents can access the information in the content (i.e., programmatically determine the information in the content) and present it to the user. For instance longdesc as an attribute should be used as a hook by user agents and asssistive technologies in order to notify the user that a long description exists, so even if longdesc is applied to an image that also serves as a link, it is programmatically determinable to separate the activation of the longdesc for exposure from the UA's universal link activation action (which is usually activated with the ENTER key, the SpaceBar, or by mouse click), so that the linked image retains the expected behavior in response to user interaction while a discrete mechanism is used to retrieve the long description. HTML4 puts it this way,"Since an IMG element may be within the content of an A element, the user agent's mechanism in the user interface for accessing the 'longdesc' resource of the former must be different than the mechanism for accessing the href resource of the latter."
- longdesc is in current use on numerous company, organizational, governmental, educational, and personal sites throughout the world.
- Some browsers support longdesc natively and are expected to continue to do so as part of their support for HTML4x. Extensions also exist.
- longdesc is implemented in numerous authoring tools.
- longdesc is implemented in popular assistive technology.
- longdesc is in numerous tutorials and documentation throughout the world.
- longdesc is in numerous guidelines throughout the world.
- longdesc is law in various countries.
- longdesc is policy in many organizations and companies in throughout the world.
- longdesc is a standard in numerous organizations and companies.
- Provides native semantics.
- PF "likes the idea of having built in semantics in HTML and in particular would prefer to have common document elements."
- A HTML attribute is easier to teach. Content creators or developers will not learn ARIA (something not native HTML). They already feel like they've learned far more than they should have to know under their job description. And in many cases, their supervisors agree. (reference Cliff Tyllick)
- It would allow longdesc to be improved. (Bug 10015: longdesc URL checking, Bug 10019: Native user agent support for exposing longdesc to all users).
- Exposition of longdesc would help authors debug. Reference: Adam Sampson.
aria-describedby is not a Functional Replacement for longdesc
- aria-describedby naively forces a visual encumbrance on sighted users.
- aria-describedby will annotate text in the target id referenced by the idref. This means assistive technology users would not be able to control how they interact with the long description (as they can with longdesc). It is read aloud without any user intervention, forcing the longer description on the user whether they want it or not.
- aria-describedby is currently limited to text that appears in the same document as the image being described.
- As, by definition, a long description is in fact long, aria-describedby is not good solution for a longdesc. (Some future feature that that moves the user's reading cursor to the longer description in a different page where the user can control how they read the long description could be a possible solution.)
- The content associated using aria-describedby as currently implemented, is limited to unstructured text. AT treats aria-describedby target content as though it does not have any mark-up. It is treated as a string of text.
- aria-describedby target content is a forced visual encumbrance on sighted users by default. Many artists, designers and marketers do not want their visual designs changed/ruined with redundant text.
- Obsolescing longdesc breaks the web for numerous company, organizational, governmental, educational, and personal sites throughout the world.
- Obsolescing longdesc would cause confusion and result in mixed messages between existing Guidelines, Laws, Policy, and Standards and HTML5.
- aria-describedby is not native HTML.
- PF "likes the idea of having built in semantics in HTML and in particular would prefer to have common document elements."
- It is unlikely that many content creators or developers will learn ARIA (something not native HTML). They already feel like they've learned far more than they should have to know under their job description. And in many cases, their supervisors agree. (reference Cliff Tyllick)
at img would also become interactive content with longdesc present. i.e. add "or longdesc" after "usemap" in the phrase "If the element has a usemap attribute" under the 'Categories' item. The longdesc attribute would be listed as an attribute for the element. i.e. Add "longdesc" to the list of content attributes, and "attribute DOMString longdesc;" to the attributes listed in the DOM Interface for the img element.
The longdesc attribute is described already in HTML 4 and the description can be re-used, although it should be made clear that the URI to which longdesc refers can be a relative reference to some part of the same page (in order to be explicit about which content is associated with the image), or a different page. I.e. in the first sentence at 1, add text such as "which may refer to a point within the current page or to a different page" after the work "link".
The example, which references an image but appears to provide useless alt text should not be copied from HTML 4.
Changes for other sections:
- 184.108.40.206.1, 220.127.116.11.2, 18.104.22.168.3 should all mention that a longdesc *may* be provided to provide a detailed description of the image, e.g. to help a person who cannot see it to find it from a description.
- 22.214.171.124.5 should mention it as a way to make the association between an image and the relevant text explicit.
- 126.96.36.199.6 should mention it as the preferred way to point to a description of the image if this is desired, rather than mis-using the alt attribute for this purpose.
- 188.8.131.52.9 should mention that where an image is a key part of the content, it should have sufficient text in the alt attribute to replace the image, and using the longdesc attribute for critical information is a mistake. However, it can be used for additional information if desired.
This has no impact on existing HTML-4 browsers, many of which fail to make longdesc accessible other than via the DOM. Failure to make this change will have an impact on assistive technologies such as screen readers, which use the longdesc attribute to find descriptions of images.
This would require conformance checking to accept the attribute as valid, and would imply maintaining the existing requirement on Authoring Tools to allow the author to use this functionality. It would maintain conformance of HTML-4 tools and content, rather than the current expected change leaving them non-conforming.
- Longdesc Examples In the Wild
- Use Cases
- Guidelines, Laws, Policy, and Standards
- Online Tutorials and Documentation
HTML 4 on longdesc
- HTML4 16.4.2 Long descriptions of frames: The longdesc attribute allows authors to make frame documents more accessible to people using non-visual user agents.
- HTML4 Index of Attributes: longdesc "link to long description (complements alt)".
- HTML4 longdesc = uri: "This attribute specifies a link to a long description of the image. This description should supplement the short description provided using the alt attribute. When the image has an associated image map, this attribute should provide information about the image map's contents. This is particularly important for server-side image maps. Since an IMG element may be within the content of an A element, the user agent's mechanism in the user interface for accessing the "longdesc" resource of the former must be different than the mechanism for accessing the href resource of the latter...The alt attribute provides a short description of the image. This should be sufficient to allow users to decide whether they want to follow the link given by the longdesc attribute to the longer description, here "sitemap.html".
- HTML4 A.3 Changes for accessibility "Authors may provide long descriptions of tables, images, and frames (see the longdesc attribute)."
HTML5 on longdesc
longdesc is currently listed as an obsolete feature in the HTML5 editor's draft. It advises to "Use a regular a element to link to the description, or (in the case of images) use an image map to provide a link from the image to the image's description."
- HTML WG Issue-30 (longdesc)
- HTML Working Group ISSUE-30: Straw Poll for Objections
- Chairs' decision on HTML WG Issue-30 (longdesc)
- Change proposal by Charles McCathieNevile
- Counter-proposal by Ian Hickson
- Change proposal: Longdesc Conforming With Warning by Maciej Stachowiak
Formal Objections to ISSUE 30 Decision
- Formal Objection, August 2010 - Leif Halvard Silli
- Notice of Impending Formal Objection to HTML5 Issue 30 Decision (@longdesc), August 2010 - John Foliot
- HTML Accessibility Task Force Teleconference discussion on longdesc, October 7, 2010
- HTML Accessibility Task Force Teleconference discussion on longdesc, December 2, 2010
- HTML Accessibility Task Force Teleconference discussion on longdesc, December 16, 2010
- HTML Accessibility Task Force Teleconference discussion on longdesc, January 6, 2011
- HTML Accessibility Task Force Teleconference discussion on longdesc, January 13, 2011
- HTML Bug 10015: longdesc URL checking - Status VERIFIED INVALID.
- HTML Bug 10016: longdesc and @role (ARIA) - Status RESOLVED WONTFIX.
- HTML Bug 10017: longdesc and @aria-describedby (ARIA) - Status VERIFIED INVALID.
- HTML Bug 10019: Native user agent support for exposing longdesc to all users - Status RESOLVED WONTFIX.
- HTML Bug 10434: Mint a link type for pointing to long descriptions (rel="longdesc") - Status RESOLVED WORKSFORME.
- HTML Bug 10455: Mint a describedby attribute for the img element - Status RESOLVED WONTFIX.
- HTML Bug 10853: HTML5 lacks a verbose description mechanism - Status RESOLVED WONTFIX.
- HTML Bug 10967: Add @desclink, a description link attr. for any embedded element + figure - Status RESOLVED WONTFIX.
- HTML Bug 11012: Also say that <area>/image maps is an alternative to @longdesc - Status: RESOLVED FIXED.