AJAX events specifications are similar to the regular POST and GET events in most areas. The few differences are highlighted here, as well as some implementation implications.

Event Source

Like with non-AJAX based events, the event source is depicted with the identity of the event source and the event type, as shown below.

       form[categoryForm].element[source element].change

For standard event, the even type must be related to server event. For AJAX event, it is a client event type that must be specified.

       form[categoryForm].element[source element].onchange

Parameters

Like non-AJAX events, parameters passed to the event need to be specified. The point of note here is the need to be more explicit in specifying parameters. For example, because the form post involves all elements in the form, the parameters for such events need not be explicit. For component based framework, the component tree is represented on the server and client side, so the issue of parameters could be implicit.

As a default it is possible to pass the page view as parameters; however performance would be enhanced if a subset is passed. This is the case, especially when the AJAX interaction involves a small fraction of components on the page.

AJAX, which is an acronym for Asynchronous JavaScript and XML, allows the creation of interactive Web applications, by allowing the exchange of data ?behind the scene? without a full page refresh.

dWebSpec provides organized means of providing specification for AJAX enabled applications.

AJAX based requests appear like any other event on the page, however there are additional implications for marking an event with the ?ajax? call option.

As discussed under the subject of element descriptor, all the dWebSpec element types have equivalent component or tag on the target platform. When an event is marked with the ?ajax? call type, for the implementation, it is the AJAX aware equivalent component that would be needed. Or else, an AJAX extender component must be associated with the component.

Except when there are no ambiguities, the event source is usually specified as (source-element.event-type). Generally the event type for standard events should be limited to server type event. For ?ajax? call type, the event type should be a client event.

As a result of the AJAX request, there is usually some level of re-rendering (partial). A segment could be designated as the target for such re-rendering. The request event id would be registered on the descriptor for such segment.

For JSF, the same principles guiding the implementations of AJAX specification applies. However, AJAX aware components are not included in the standard reference implementation. This subject is discussed in this section for the Seam platform. The components discussed therein are generally applicable to AJAX reference implementation.