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The Cascading Action System
The majority of the Note revolves around what the authors call the
Cascading Action System (CAS). This is simply an example Action System, and
is fully defined in Appendix 2 of the Note. At a basic level, the Cascading
Action System is simply an application of CSS-derived concepts to the realm
of scripting languages.
For example, selectors under CAS are defined to be identical to those in
CSS2, both in their scope and their flexibility. Class selectors, ID
selectors, element selectors, and selector grouping are all exactly the
same as you would expect under CSS2. Thus, you could define a hover-style
effect for anchors by declaring:
A *[HREF] {onMouseOver: "this.style.fontColor = 'cyan'";}
Of course, there are differences in the rules for scripting actions.
Instead of CSS properties, there are actions such as onMouseOver,
as seen in the above example. As a matter of fact, the possible actions
(the action domain for CAS) are the event handlers defined in HTML
4.0:
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CAS Event Handlers
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onLoad
onUnload
onCLick
onDblClick
onMouseDown
onMouseUp
onMouseOver
onMouseMove
onMouseOut
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onFocus
onBlur
onKeyPress
onKeyDown
onKeyUp
onSubmit
onReset
onSelect
onChange
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As for the structure of a CAS Action Sheet itself, it's amazingly simple.
There are only three CAS tags defined in the Note: actionsheet,
action, and script. Of these, only the last two accept
any attributes.
For action, the possible attributes are
type, which is used to define the Action System in use, and
codetype, the value of which is the name of a scripting language
such as text/javascript.
In the case of script, there are three attributes: type,
which is the same as codetype is for action,
src, which can be used to give the URI of a document contained
scripts, and charset, which specifies the character encoding of
the script; for example, charset="iso-8859-1", which would
define the script's character set to the the Latin-1 charset, the most
common set in use on the Web.
But enough theory, let's see CAS in action (if you'll pardon the pun).
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