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Discussion Page for LONGDESC Retention Change Proposal

The following is supplemental and historical information which is directly related to the proposal to retain LONGDESC and some practical implementation suggestions. More information about LONGDESC discussions prior to the lodging of this change proposal is also available on this wiki.


The purpose of LONGDESC is to describe the contents of the image as fully and completely as possible.

Gregory J. Rosmaita's Original Rationale for Retention

There are many compelling arguments for the retention of the LONGDESC attribute, as defined in HTML 4.01 Strict. A mainstream arguement for LONGDESC is that there is a moral and often legal need for it amongst academics, educational institutions, and government entities, as more and more course content migrates to the web or intranets, equal access demands that they provide a meaningful long description.

Academics constantly complain to me that if they are to teach students without vision or with very low vision, they need more than ALT or CAPTION -- they need to describe the subtleties of the image being presented as content for those who cannot see the content, and those who have found a longdescription helpful, as a key to the symbolism contained in the image; or as a means of expounding on a static image of a map (such as of a migration, a battlefield, a schematic of a subway system, etc.)

The following is an example of the difference between a caption for an image, and a long description of that image. The image in question is an image of the British flag; the occasion? As an illustration accompanying an article on the 200th anniversary of the formation of the United Kingdom. Such a caption might read:

The Flag of Union has been the official flag of the United Kingdom since the Act of Union of 1807, which created the modern political entity known as the United Kingdom, which, this year, celebrates its 200th anniversary.

Now, compare that to the following LONGDESC:

The Flag of Union has been the official flag of the United Kingdom since the Act of Union of 1807, which created the modern political entity known as the United Kingdom, which, this year, celebrates its 200th anniversary.

The flag of the United Kingdom is commonly known as the Union Flag, or Union Jack. It is the national flag of the United Kingdom of Great Britain and Northern Ireland. The flag's design dates from January 1, 1801, as a symbol of the Act of Union of 1800, which merged the Kingdom of Ireland and the Kingdom of Great Britain (until 1707, the United Kingdoms of England and Scotland), to form the United Kingdom of Great Britain and Ireland.

The flag symbolically uses the national flags of England, Scotland, and Ireland to form a single flag comprised of:

  • the flag of Scotland, which bears Saint Andrew's cross: a white X on a blue field; and
  • the flag of Ireland, which bears Saint Patrick's cross: a red X on a white field;
  • the flag of England, which bears Saint George's cross: a red cross on a white field;

The flag of Scotland forms the bottom layer of the Union Flag. Over Saint Andrew's white cross, the red cross of Saint Patrick is superimposed, on top of which is a white-bounded red cross of Saint George.

Now that is a world of difference. A caption pre-supposes that one can also perceive the object being captioned (that is, put into context); just as a TABLE without a summary pre-supposes that one can also perceive the data sets being table-ized.

Just as the contents of the summary attribute can be reused to provide a visual rendering of the summary's contents, so too can a LONGDESC be yanked into an IFRAME (not my preference) or embedded as an OBJECT by the browser, so as to replace the image inline. (Note: the browser should offer at least the following choices: show images, show LONGDESC, show ALT text, but both ALT and LONGDESC should be available whether image loading is turned on or off, something over which, in a locked-down setting, the user may have no control)

LONGDESC, would, perhaps, have more mainstream support if the attribute used to point to a long description was HREF and not LONGDESC -- even HREFDESC would have been a more implemented iteration of LONGDESC as it is defined in HTML 4.01 (where hrefdesc is an attribute such as hreflang)

The unquestioning bending to the marketplace's will, by claiming that, since LONGDESC is not widely implemented, it should be deprecated, when it must be remembered that one of the major reasons it is not more widely supported by mainstream apps, is due to simple "market realities" -- there aren't enough of us who need LONGDESC and summary to market to, and therefore, any additional work that would inherently increase the accessibility of the product isn't needed or is assumed to be exclusively a third-party slash assisstive technology's responsibility.

Every day you age, your eyesight becomes a little less sharp than it once was, and if you survive to a ripe old age, you, too, may be dependent upon summaries for tables and long descriptions for graphical objects...

source: Gregory J. Rosmaita post to public-html, 24 June 2007

Usefulness of LONGDESC in the Digitization of Books & Historical Works

LONGDESC is indispensable for anyone attempting to perform serious academic work via the web. Increasingly, colleges and universities are incorporating online ciriccula into all aspects of learning -- on campus, off-campus, long-distance, etc. In many jurisdictions, this means ensuring equal access to all course content - consult: Policies Relating to Web Accessibility

What follows is an example drawn from real life:

When encountering a portrait of Lord Cornwallis, it isn't sufficient to simply caption the image "Portrait of Lord Cornwallis, ca. 1774" -- the student of the subject needs to know precisely how Lord Cornwallis is portrayed -- how old was he at the time of the portrait? what kind of hairstyle does he sport? What type of uniform? What do the buttons on the uniform signify? What is his rank, based on the eppalettes? What are the items that are included in the portrait, particularly those held by, or within reach of, the portrait's subject, for all such items have both symbolic and highly specific meanings, all of which the painter assumed would be understood by the viewer.

Any reference material worth its weight in bytes must include LONGDESC so that the specifics of the image can be conveyed as completely and as thuroughly as would a careful, informed study of the actual portrait.

source: Gregory J. Rosmaita, post to public-html (24 June 2007)

Strategies for Exposing LONGDESC

The first thing a screen-reader, or other assisstive technology, must do when it discerns the presence of a longdesc target is: alert the user that it is there.

The second thing a screen-reader or other assisstive technology must do when it discerns the presence of a longdesc target is to allow the user to activate that target, if that is the user's wish, so as to expose the contents of the longdesc document. Ever since it began to support longdesc, JAWS for Windows alerts the user to the presence of a long description, and prompts the user (in basic mode) to hit ENTER, and the contents of the longdesc document associated with the image is displayed in a pop-up window (not the best solution when the default for a lot of programs these days is block all popups) and the User Agent Accessibility Guidelines (UAAG) strongly discourages the opening of new browser instances without warning the user that it is about to do so, and without the option of opening in a new tab or in the viewport of the original document.

The last thing that needs to be done is to provide a mechanism to return to the document in which the described image is embedded.

Obviously, Step 1 is the responsibility of the assisstive technology, but the under-the-hood mechanics of exposing descriptive content SHOULD be the user agent's responsibility; This issue is directly addressed in UAAG Guideline 2, Checkpoint 2.5 -- a Priority 1 checkpoint

What is needed, therefore, is a normative list of recommended/expected actions that allow multi-modal interaction with the long description.

Treating LONGDESC as HREF isn't the only means of exposing the content of the long description page; the contents -- or the main portion thereof -- could be rendered inline instead of the image or in an IFRAME (which has its own accessibility issues) or any other number of means of exposure.

The key is that the UA should support LONGDESC natively, and allow the user a set of choices about exposing LONGDESC:

  • expose in new browser instance
  • expose in new browser tab
  • expose inline (insert content as object)
  • expose inline through the use of IFrame
  • expose the contents of the longdesc document in a side-bar, aligned with the image it describes

and there are many other options, provided a user knows what to do when encountering a long description, then it matters not what assisstive technology she is using, for there is an expected action in the case of browser x for exposing LONGDESC

source: Gregory J. Rosmaita, post to public-html (24 June 2007)