Ajax (an acronym for Asynchronous JavaScript and XML) is a group of interrelated web development techniques used on the client-side to create asynchronous web applications. With Ajax, web applications can send data to, and retrieve data from, a server asynchronously (in the background) without interfering with the display and behavior of the existing page.

Salesforce has developed the AJAX tool for developers to help them make a simple and easy Re-render Command button or command link using tag attribute. This tool can go directly to the server and can refresh only the relevant parts of the request. It is a great solution to facilitate the work of the developers but it was limited to few request.

BA Link was engaged in an implementation for a large Salesforce client. In their environment, the use of AJAX in the context of developing highly rich pages or in the element action function, had for result to impair the page as well as cause other errors. This problem is usually featured by the loss of the page or the inability for it to render the desired part.

The way our team approached this challenge was by reverting to the classic AJAX using JScalls : an external page where it is possible to ask what is required and get the answer to blockHTML, XML, or. JSON.

The advantages:
1. No restriction in the number of read requests; each page individually performed a new query.
2. The Page itself produced by Salesforce is much more “easy” because there is no addition of automatic code.
3. Performing multiple reading asynchronously

News & related information:
Salesforce last version came out with a new tool under the name Ajax remote, more info on: http://wiki.developerforce.com/page/Ajax_Proxy