The Event Broker is ideally suited to situations where you need to modify the browser's Document Object Model (DOM), but using data from your back-end server.

A good example is the automation and in-browser validation of a form containing postal address information. Imagine you want the user to enter the postcode or zipcode. You then want to check that the postcode/zipcode is valid, and if so, automatically fill in all the relevant address fields for the user.

Clearly you can't validate the postcode/zipcode locally within the browser using Javascript - the lookup table would be much too large to send to the browser. This would therefore normally require the submission of the form to the back-end, but with the Event Broker you can do all this without refreshing the page. What we can do is add an onChange Event Handler to the postcode/zipcode field and get it to make an Event Broker call to a server-side function that validates the value entered by the user. If invalid, the back-end function can return a Javascript alert. If valid, the back-end function can look up the address field data for the postcode/zipcode entered by the user, and return a string of Javascript commands that will modify the values of the form fields that should hold those values.