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Verbose desc reqs

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Verbose (As Long As Necessary) Descriptor Requirements

Note The content of this document was submitted to the HTML WG as Issue 30 Change Proposal: Include longdesc in HTML5. Please consult that document for the most recent data, additional information, rationale, and updated links.

Also see HTML WG Bug 10853: HTML5 lacks a verbose description mechanism and other bugs.

Issue

HTML5 does not provide the functions that had been provided through the HTML 4 attribute longdesc. Those functions are:

  1. A direct, reusable programmatically determinable mechanism to a long description of an image without a forced visual encumbrance or default visual indicator.
  2. A method to reference a longer description of an image, without including the content in the main flow of a page.

Many images cannot be sufficiently described with other long description techniques. For instance, longdesc currently provides a solution for describing the content of images to the blind when it would be:

  • Visually apparent and redundant to a sighted person.
  • Unacceptable to the marketing department due to aesthetic considerations.

Purpose

The purpose of a verbose descriptor is to describe an image. Such a description is essential for users who can not see, but who need access to information contained in a graphic.

While verbose descriptors provide an important accommodation for the blind and visually impaired, a verbose descriptor may also be used by those with an extremely limited viewport or with cognitive difficulties as a guide to navigating and comprehending the described image. This means that the exposition of a verbose descriptor must not be an "either-or" proposition; rather, the user should be able to control the means of exposing the verbose descriptor, including the ability to simultaneously view the contents of the image and the contents of the verbose description.

Programmatically Determinable

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."

Use Cases

Uses cases have been identified that specifically require longdesc.

Formal Use Cases Requiring longdesc

For formal use cases, please visit Long Description Research: Use Cases. They include:

  1. Logo-A-Go-Go
  2. Artistic Principles
  3. No Link Can Serve Two Masters
  4. Accessibility While Mitigating Browser Damages
  5. This is By Design
  6. Something for Everyone, not Everything for Anyone
  7. Efficiency Through Recycling
  8. Basic HTML Authors or "ARIA is not in my Job Description"

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 natively 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 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 (longdesc is not hidden meta-data) 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.

Usage

Numbers alone must not be the driving factor for technology decisions. Both mainstream (80/20) and edge-case requirements must be addressed, because for online information, there is:

  1. No standardized user, and
  2. No standardized device (browser or other user agent) for accessing information.

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.

Obsoleting longdesc Breaks the Web

The longdesc attribute is in current use on company, organizational, governmental, educational, and personal sites throughout the world, including but not limited to:

  • Argentina
  • Australia
  • Austria
  • Belgium
  • Canada
  • China
  • England
  • France
  • Germany
  • Ireland
  • Italy
  • Japan
  • Myanmar
  • New Zealand
  • Portugal
  • Spain
  • South Korea
  • United Kingdom
  • United States

Obsoleting longdesc specifically breaks the web for over 150 sites in the wild that are using it to describe images. Both authors and users have expectations that longdesc will continue to support existing content.

Requirements

Discoverable:
The consumers of complex images will often require a programmatic mechanism to reference a longer textual description, either internal or external to the document containing the described image. This mechanism MUST provide a programmatic means of informing users and authors that a description is present/available, while at the same time provide user control over exposition of the descriptor, so that rendering of the image and its description is not an either/or proposition. (A visual indicator of the description SHOULD NOT be a forced visual encumbrance on sighted users by default).
Actionable:
Upon discovery, the end user will require a device independent way to access the descriptive content: the longer textual description MUST NOT be forced upon the end user, but only offered as a choice. There is an explicit provision that accessing descriptive content, whether internal or external to the document containing the image, MUST NOT take the user away from the user's position in the document containing the image where the verbose descriptor was invoked. Finally, 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 verbose descriptor resource of the former MUST be different than the mechanism for accessing the href resource of the latter.
Supports Structured Mark-up:
A longer textual description of a complex image MUST be capable of supporting structured mark-up (for example a pie-chart could be expressed as tabular data using actual <table> markup).
Portability / Re-Use:
The programmatic mechanism MUST provide a method to reference a longer description of an image, without including the content in the main flow of a page.
Backwards Compatibility & Ease of Use:
Any new mechanism MUST include a means of accessing content added by authors using the HTML4 attribute longdesc (backwards-compatibility for "legacy" content). Accessing the longer textual description SHOULD be easy to author, easy to maintain, and be easy for the end user to interact with.

Satisfying These Requirements for HTML5

Below are several possible engineering approaches to meeting the requirements above. Some approaches stand by themselves and would meet the requirements. Several approaches are described in order to provide maximum flexibility with respect to other engineering constraints. The goal is to meet the requirements above.

Reinstate longdesc

Retain support for longdesc; allow for exposition of longdesc via user agent preference, context menu, or toggle inline as well as for simultaneous exposition of both the image and its description (useful for those with very limited viewports or users with cognitive issues, or authors for authoring and maintenance purposes). (Reference: Bug 10019 - Native user agent support for exposing longdesc to all users).

Use aria-describedby and Deprecate longdesc

Add support for aria-describedby and deprecate longdesc in HTML5.

  • disadvantage: aria-describedby does not provide a functional replacement for longdesc.
  • disadvantage: Naively forces a visual encumbrance on sighted users.
  • disadvantage: 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.
  • disadvantage: aria-describedby is currently limited to text that appears in the same document as the image being described.
  • disadvantage: 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.)
  • disadvantage: 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.
  • disadvantage: 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.
  • disadvantage: Obsolescing longdesc breaks the web for numerous company, organizational, governmental, educational, and personal sites throughout the world.
  • disadvantage: Obsolescing longdesc would cause confusion and result in mixed messages between existing Guidelines, Laws, Policy, and Standards and HTML5.
  • disadvantage: aria-describedby is not native HTML.
  • disadvantage: PF "likes the idea of having built in semantics in HTML and in particular would prefer to have common document elements."
  • disadvantage: 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)

Add Support for External References and Structured Content to aria-describedby and Deprecate longdesc

Add a Native describedby Attribute

A bug was filed on August 26, 2010 to create a new HTML attribute. It is Bug 10455: Mint a describedby attribute for the img element. It could be named something else if desired (ie "describedat" or "closeddescription" or "cdescription" or "closeddesc" or "cdesc" (invisible by default like a television closed-caption but can be opened via the user agent).

Reinstate longdesc and Add a Native describedby Attribute

Retain support for longdesc as a reference for external URIs, and add a native describedby attribute for the img element (Bug 10455) attribute with which to internally reference structured content to provide a verbose description through a string of space separated IDREFs.

  • longdesc must allow for exposition of longdesc via user agent preference: context menu or toggle inline, as well as for simultaneous exposition of both the image and its description (useful for those with very limited viewports or users with cognitive issues, who may need a description's guide to assist in the user's understanding of the image being described) (Reference: Bug 10019 - Native user agent support for exposing longdesc to all users);
  • describedby must allow structured content to be referenced via id; a native describedby attribute would make possible the referencing of distinct portions of a page, which -- when combined -- form a suitable verbose description of the image being described; (for example, <describedby="#foo1 #foo2 #foo3">; this will make it possible for assisitive technologies to conflate each referenced portion of the internal document into a single verbose description of the image, and can be used for the benefit of those who do not use assistive technology through the use of CSS to bind the image being described with its full description.

Use aria-describedby for internal description references and create aria-describedat for external description references

Recently, PFWG has discussed introducing a new ARIA attribute, aria-describedat, as a possible addition to a future ARIA specification (ARIA 1.1) for external descriptions.

@@ Fill out this section with discussion from Face to face meeting 2 November 2011 (Note: This is a private PF member only link. Regular task force members can not access it.)

This recent change of focus represents an acknowledgment that the idea to use aria-describedby could not have technically worked.

The main purpose of aria is to generalize functionality already present: aria-label can be used instead of alt, and on all elements. But, despite that, aria-label has not lead to deletion of alt. Likewise possible introduction of aria-describedat in a future ARIA version, does not require the abolition of longdesc. Rather, it acknowledges that the idea behind longdesc is good. The alt attribute also has some features that aria-label does not have - such as that it works in any User agent (UA) with images disabled. Likewise, longdesc already works in many UAs - whereas aria-describedat would not work in the same UAs. In sum:

Implementation Information for LONGDESC

NOTE: This section is under construction -- all vanilla text will be replaced by links to pertinent information. Feel free to add any pertinent info or correct what appears below.

The following content is drawn from research by Laura Carlson and John Foliot -- especially Laura's original list of tools

User Agents/Browser Support for LONGDESC

Opera, Firefox, Chromium, and Internet Explorer all support longdesc DOM reflection.

  • 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 IMG for 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
  • SeaMonkey -- discloses longdesc URI via <right-click>/<properties>/Description
  • WebbIE

Authoring Tool Support for LONGDESC

Assistive Technology Support for LONGDESC

Other Tool Support for LONGDESC

Research

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)."

Hidden Meta-data Fallacy

Longdesc as "hidden meta-data" is a fallacy. The term "hidden meta-data" is pejorative, and not an accurate description of attributes such as longdesc. Rather the term should be "discoverable meta-data", which means access should be in accordance with a user's individual preferences. User Agents and authoring tools can and should offer a preference to provide access in accord with user preference.

Germane to the "hidden meta-data" fallacy is the fact that the Web is not a visual medium. It never has been. It's an electronic communication medium, both audio and visual, both print and screen etc. Even though the majority of users have vision and use visual means to access content doesn't make the web a visual medium. It is multi-modal. Perhaps some web developers concentrate on a particular media type more than another. And perhaps on many web sites, sighted, dexterous, able-bodied users outnumber users with a disability. But the strengths of the web, which makes it unique as a medium of communication, is that it isn't limited to a single output. That is the beauty.

One Size Doesn't Always Fit All

The primary markup language of the World Wide Web should aim to extend the range of communication and make the web more accessible, universal, and inclusive. This however, does not equate to one size always fitting everyone. Two quotes sum this idea up:

accessibility is something for everyone, not everything for anyone, it's the content that's important not the interface - Adrian Higginbotham
The rationale for personalisation for accessibility is clear. Accessibility is essentially dealing with diversity - personalisation avoids the always flawed attempt of doing so by a "one size fits all" solution. - Martyn Cooper

Ensuring access to information for those who would otherwise be locked out and lose their opportunity to use the Web is the socially responsible and right thing to do.

Because one size doesn't always fit all, HTML5 should not obsolete features if not all users can fully make use of them but rather alternative/equivalent mechanisms like longdesc should be provided. It is a needed accommodation mechanism.

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."

References

Related Resources

Issue 30

Previous Proposals

Previous Recommendations

Formal Objections to ISSUE 30 Decision

Minutes

Related Bugs

  1. HTML Bug 10015: longdesc URL checking - Status VERIFIED INVALID.
  2. HTML Bug 10016: longdesc and @role (ARIA) - Status RESOLVED WONTFIX.
  3. HTML Bug 10017: longdesc and @aria-describedby (ARIA) - Status VERIFIED INVALID.
  4. HTML Bug 10019: Native user agent support for exposing longdesc to all users - Status RESOLVED WONTFIX.
  5. HTML Bug 10434: Mint a link type for pointing to long descriptions (rel="longdesc") - Status RESOLVED WORKSFORME.
  6. HTML Bug 10455: Mint a describedby attribute for the img element - Status RESOLVED WONTFIX.
  7. HTML Bug 10853: HTML5 lacks a verbose description mechanism - Status RESOLVED WONTFIX.
  8. HTML Bug 10967: Add @desclink, a description link attr. for any embedded element + figure - Status RESOLVED WONTFIX.
  9. HTML Bug 11012: Also say that <area>/image maps is an alternative to @longdesc - Status: RESOLVED FIXED.

Glossary

Functional Replacement
a solution that provides the same utility that the current (longdesc) solution provides.
Programmatically Determinable
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 assistive 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."
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