new html extension proposal

AChen@jgc.com
Mon, 21 Aug 95 09:28:32 PST

I would like to propose a new extension to HTML, the X-ALTSRC
attribute in the <IMG> tag. Currently, many of the major browser
companies, such as Netscape and America Online support this extension.

Its general form is: <IMG X-ALTSRC="[mime/type;]URL"> When used in
conjunction with the SRC attribute, this new attribute allows users to
specify an alternate source file that can be used to display a graphic
image.

Here's an example:
<IMG
SRC="/images/daytona.gif"
X-ALTSRC="/images/daytona.abc"
>

In this case, ABC-enabled browsers would read the entire IMG tag and
use /images/daytona.abc instead of /images/daytona.gif. Old-style
browsers, who know nothing of X-ALTSRC, would use /images/daytona.gif.
This format is called "dual encoding.

The optional [mime/type;] portion of the attribute lets a user
explicitly tell the browser the format of the file that follows,
rather than having the browser determine the format based on the file
extension, its default behavior. Here's a variation of the previous
example that illustrates how it works:

<IMG
SRC="/images/daytona.gif"
X-ALTSRC="image/x-abc;/images/daytona.v1" >

In this case, the browser knows that the file format is ABC-based on
the mime/type, and the file extension is ignored.

Feedback ... comments? What is the next step from here? Is there a
formal procedure to go through?

thanks,

Albert Chen