Backplane: Events

Steven Pemberton, CWI/W3C, Amsterdam

Events

Within W3C and outside, much use is being made of events and event handling.

Specs such as HTML and XForms use events as the hook for adding interactive functionality, and defining the processing model through sequences of events.

And then there are:

• DOM3 events
• XML Events 2
• Abstract or intent-based events
• Events over the wire
• XML Handlers
• CSS Events
• XBL Eventing
• Remote Events for XML (REX) Requirements

W3C WGs

Events are important to many groups, especially those related to interactive content.

Groups that are clearly involved include: HTML, Forms, SVG, WAI, Voice, SYMM, DI, CDF and Web API.

What is needed is a unified approach across W3C, preferably in a generic way so that compound documents can operate in a consistent manner.

Topics

Topics that have to be addressed in the events area include:

• Device independence
• Accessible eventing
• Standard events for frequently occurring use cases.
• XML-generic markup for handlers
• Scripted and declarative handlers
• Methods for binding events and handlers
• Security issues when binding cross-document
• Cross-namespace issues in compound documents
• Integrating event approaches (such as merging SMIL and Voice/CCXML events with the DOM approach).

Device independence/Accessibility

A prime example of this is the difference between a click on a link and activating a link (which can happen via different approaches).

Similarly you want to unlink the connection between how someone scrolls down, and the act of scrolling down, or how someone asks for help, or exits, or ...

This is closely related to accessibility for events as well.

XML Generic Markup

HTML/XHTML/SVG have markup for binding to handlers via <script>.

XML Events is a generic syntactic binding to DOM 2 events, but it is (deliberately) vague about what a handler looks like.

We need a W3C-wide markup for handlers.

Conclusion

A backplane for event handling would be based on DOM 3 events, and allow a multi-namespace document to communicate over all the subparts using the same event mechanism.