[This is preliminary documentation and subject to change.]
The STATE_SYSTEM_ANIMATED flag is used to mark an object whose appearance is changing rapidly or constantly. Blind access utilities can use this flag to avoid notifying the user repeatedly for what is really a single series of visual changes.
A special case of this is marquee text; that is, text that is progressively disclosed as it scrolls across a region. Such objects should be given the attribute of STATE_SYSTEM_ANIMATED. In most cases the object's Value property string should reflect the entire text, even the portion that is not currently visible. If the Value string is changed too frequently, a blind access utility might not be able to convey it usefully to the user.
Example: A window contains a rectangular region in that shows the word "Cool!" moving around in a figure-eight pattern. (This can be implemented using AVI files or through other means.) This object's Role property would be GRAPHIC, its Value property would be the string displayed, and its LOCATION would be the bounding rectangle, and it would have the STATE_SYSTEM_ANIMATED attribute flag set. (STATECHANGE events would also be generated when the object started or ceased animating.) Its Description property should also be something like "The word 'Cool!' is moving about the screen in a figure-eight pattern."