Understanding how a HATS application works

To understand the purpose of the customization techniques described in this chapter, and how they work together, you must first understand how a HATS application processes a host screen to convert it to a GUI. When a user accesses a HATS application, a request is sent to the HATS application, running on a WebSphere® Application Server, a WebSphere® Portal, or a rich client platform. The HATS application forwards the request to the host application and receives a host screen. The HATS application transforms the host screen, using the customization you have created in the HATS project, and sends the transformation to the user. Each time the user interacts with the HATS application, the process is repeated.

The HATS application uses a rules-based approach to determine how to convert each host screen. HATS applications can contain a list of screen events (screen customizations and screen combinations), which specify criteria used to match host screens. Each screen event also lists actions to be taken when a match is found. Your HATS application compares each host screen to its ordered set of screen events, and when the first match is found, it performs the specified actions. You do not have to specify how to convert every single screen from your host application. If there is no matching screen event for a host screen, HATS performs the actions defined for the unmatched screen application event, which by default applies the default transformation. See Working with screen events for more information.