XML Events

Adding Behavior To XML Content
T. V. Raman
IBM Research

Outline

  • Motivation.
  • DOM2 Interface EventListener .
  • Authoring EventListener via XML.
  • Bringing XML content to life via the DOM.

1

Motivation
Bring Static XML To Life

2

XML 1.0

Universal syntax for communicating S-expressions.
  • Can encode structured data.
  • Can encode structured documents.
  • Enable self-describing content.

3

Syntactic Expressions

Come to life when bound to behaviors.
  • Semantics implemented by consumer.
  • XML separates data from behavior.

4

Example

    <person>...</person>

Possible behaviors include:

  • Insert appropriate record into a database.
  • Generate human-readable display.
  • Generate user interface to edit person.

Attached behavior determines interaction semantics.

5

DOM2 Events

6

Interface EventListener

Defines event dispatch for XML browsers.
  • Provides generic eventing framework.
  • Generalizes HTML eventing mechanism.
  • Framework for adding behavior to XML.

7

DOM2 Event Propagation

html head … body … a click here …

8

DOM2 Event Propagation

Event flow when click here is activated.
  • User agent propagates event:
    • Caputre —Event travels from root to target,
    • Target —Event arrives at the target,
    • Bubble —event bubbles back to the root.

Observers can attach to nodes on path the event travels.

9

DOM2 Events Features

  • A generic event system,
  • Register event listeners and handlers,
  • Route events through a tree structure,
  • Access to context information for each event,
  • Definition of event flow.

10

XML Events

11

Goals

  • Expose DOM event model via XML markup.
  • Extend events without modifying DTD.
  • Integrate with other XML languages.

12

Authoring Behavior Via XML Events

Authoring —specify a (element, event, handler) triple.
  • 〈listener〉 —directly specify the triple.
  • Observer —attributes specify event, handler.
  • Handler —attributes specify event, observer.

13

Specifying Triple Explicitly

  <listener event="activate"  
  observer="button1"  
  handler="#doit"/>

  • Call handler identified by #doit
  • When event activate occurs
  • On element id=button1
  • Or any of its children.

14

Stopping Event Propagation

<listener propagate="stop"  
  event="activate" observer="block"  
  handler="popup" phase="capture"/>

  • Call handler id=popup
  • when block receives event activate.
  • Stop further propagation of this event.

15

Attaching Attributes To Observer

Events can be authored directly on the observer element.
<anyelement ev:event="ev:click"  
  ev:handler="#clicker"/>

<a href="doc.html"  
  ev:defaultAction="cancel"  
  ev:event="activate"  
  ev:handler="#popper">  
  The document</a>  
  

16

Attaching Attributes To The Handler

Handler can carry event attributes.
<script type="..." ev:event="submit"  
  ev:observer="form1">  
  return docheck(event);  
</script>
  • Declares script handler for event submit
  • Arriving at element id="form1".

17

XHTML
Generic Application Container

18

XHTML 1.1

XHTML 1.1 —Generic Application Container.
  • Can host multiple namespaces.
  • Presentation can be styled.
  • Can be brought to life via events.

19

XML Vocabularies

XML vocabularies define domain-specific markup.
  • Define constructs for encoding data.
  • Declarative event handlers.
  • Modality-specific event types.
  • Use XML events to bind these handlers.

Turn XHTML browser into an application container.

20

PIC

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