Web and Software: Definitions

Still working on this definition. Submit placeholder only.

Note: This is not intended to apply to text editors like Notepad. Concern that this will be too broadly applied due to the definition of "content". Subcommittee still working on these concerns.

Concern that there is no consideration for frequency here. Auto-updating at very slow frequencies like once per day is not a problem. Concern that this is too broad and will cause ARIA content to fail even when there is no problem.

• Note 1: If there is a direct route from the application to the underlying layer then the software components in the middle are not considered to be a "platform". For example, a program which hosts plug-in's is not a platform if the plug-in can directly access the underlying layer.
• Note 2: An application offering a compute service, such as a 3d rendering engine where a requesting application can directly access the underlying layer would also not be considered a "platform".
• Note 3: A particular software component may play the role of a platform in some situations and not in others. Platforms can include such things as Internet browsers, operating systems, plug-ins to internet browsers or other software applications, and under some situations, byte-code interpreted virtual environments, and other "programming within another programming" environments.
• TBD: Notes about bootloader programs and closed systems?

alternate proposal: collection of software components that runs on an underlying software or hardware layer, and that provides a set of software services to applications which allows them to be isolated from the underlying software or hardware layer.

• Note 1: For our purposes, it is those software components/services provided to applications for the creation or manipulation of user interfaces and user input - that impact accessibility - which are of concern for whether something is a platform or not. An application offering a compute service, such as a 3d rendering engine where a requesting application isn't using the software components/services to create a user interface and interact with the user, should not be considered a "platform".
• Note 2: If applications typically connect directly to the underlying layer, rather than relying solely on the platform software components and services, then it is likely that the software components in the middle are not acting as a "platform". For example, a program which hosts plug-in's is not a platform if the plug-in can directly access the underlying layer.
• Note 3: A particular software component may play the role of a platform in some situations and not in others. Platforms can include such things as Internet browsers, operating systems, plug-ins to internet browsers or other software applications, and under some situations, byte-code interpreted virtual environments, and other "programming within another programming" environments.

• Note: Although any "other resources" would be rendered together with the primary resource, they would not necessarily be rendered simultaneously with each other.
• Example 1: When you enter http://shopping.example.com/ in your browser you enter a movie-like interactive shopping environment where you visually move about a store dragging products off of the shelves around you into a visual shopping cart in front of you. Clicking on a product causes it to be

demonstrated with a specification sheet floating alongside.

• Example 2: A Web resource including all embedded images and media.
• Example 3: A Web mail program built using Asynchronous JavaScript and XML (AJAX). The program lives entirely at http://mail.example.com, but includes an inbox, a contacts area and a calendar. Links or buttons are provided that cause the the inbox, contacts, or calendar to display, but do not change the URL of the page as a whole.
• Example 4: A customizable portal site, where users can choose content to display from a set of different content modules.

Include a placeholder only for this definition.

Alternate proposal: Remove as this is not used in any provisions.

Alternate proposal: Remove as this is not used in any provisions.

Note: This is not intended to apply to text editors like Notepad. Concern that this will be too broadly applied due to the definition of "content". Subcommittee still working on these concerns.

Concern that there is no consideration for frequency here. Auto-updating at very slow frequencies like once per day is not a problem. Concern that this is too broad and will cause ARIA content to fail even when there is no problem.

• L1 is the relative luminance of the lighter of the foreground or background colors, and
• L2 is the relative luminance of the darker of the foreground or background colors.

Note 1: Contrast ratios can range from 1 to 21 (commonly written 1:1 to 21:1).

Note 2: For dithered colors, use the average values of the colors that are dithered (average R, average G, and average B).

Note 3: Text can be evaluated with anti-aliasing turned off.

Note 4: Background color is the specified color of content over which the text is to be rendered in normal usage. If no background color is specified, then white is assumed.

Note 5: For text displayed over gradients and background images, authors should ensure that sufficient contrast exists for each part of each character in the content.

1. there are more than three flashes within any one-second period; and
2. the flashing is below 50 Hz; and
3. the combined area of flashes occurring concurrently and contiguously occupies more than a total of .006 steradians (25% of any 10 degree visual field on the screen).

For the general flash threshold, a flash is defined as a pair of opposing changes in relative luminance of 10% or more and the relative luminance of the darker image is below 0.80. An "opposing change" is an increase followed by a decrease, or a decrease followed by an increase.

For the red flash threshold, a flash is defined as any transition to or from a saturated red.

• Note 1: For general Web content, using a 341 x 256 pixel rectangle anywhere on the displayed screen area when the content is viewed at 1024 x 768 pixels will provide a good estimate of a 10 degree visual field for standard screen sizes and viewing distances.

• Note 1: Fonts with extraordinarily thin strokes or unusual features and characteristics that reduce the familiarity of their letter forms are harder to read, especially at lower contrast levels.
• Note 2: Font size is the size when the content is delivered. It does not include resizing that may be done by a user.

Note 1: The relative luminance of an sRGB color is defined as L = 0.2126 * R + 0.7152 * G + 0.0722 * B where R, G and B are defined as:

• if RsRGB <= 0.03928 then R = RsRGB/12.92 else R = ((RsRGB+0.055)/1.055) ^ 2.4
• if GsRGB <= 0.03928 then G = GsRGB/12.92 else G = ((GsRGB+0.055)/1.055) ^ 2.4
• if BsRGB <= 0.03928 then B = BsRGB/12.92 else B = ((BsRGB+0.055)/1.055) ^ 2.4 and RsRGB, GsRGB, and BsRGB are defined as:
  • RsRGB = R8bit/255
  • GsRGB = G8bit/255
  • BsRGB = B8bit/255

The "^" character is the exponentiation operator. (Formula taken from [sRGB] and [IEC-4WD]).

Note 2: Almost all systems used today to view Web content assume sRGB encoding. Unless it is known that another color space will be used to process and display the content, authors should evaluate using sRGB colorspace. If using other color spaces, see Understanding Success Criterion 1.4.3.

Note 3: For dithered colors, use average values of the colors used (average R, average G, and average B).

Note 4: Tools are available that automatically do the calculations when testing contrast and flash.

Note 5: A MathML version of the relative luminance definition is available.