WAP Push is based on the traditional client/server model but in contrast to the ordinary pull technology there is no explicit request from the client before the server transmits its content.A push operation in WAP is accomplished by allowing a Push Initiator (PI) to transmit push content and delivery instructions to a Push Proxy Gateway (PPG), which then delivers the push content to the WAP client according to the delivery instructions. The PPG is typically a WAP Push Gateway with support for WAP Push. The PI is typically an application that runs on an ordinary web server. It communicates with the PPG using the Push Access Protocol (PAP). The PPG uses the Push Over-the-Air (OTA) Protocol to deliver the push content to the client. PAP is based on standard Internet protocols. XML is used to express the delivery instructions, and the push content can be any MIME media type. This SDK supports PAP 1.0 for all the standard operations with the exception of Client Query Capabilities. PAP 1.0 allows any content type to be pushed to the WAP client. However, the client may not be able to receive them. The WAP standard defines three push content types, which are supported by this SDK: Service Indication (SI) – send a notification to the WAP client. Service Loading (SL) – cause the WAP client to load and execute a service.
Cache Operations (CO) – invalidate content objects in the WAP client cache.
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