Chapter  5: Creating HDML Services that "Push" Information

The conventional Web model is a synchronous model, in which the user iteratively requests information, which Web servers supply. This model requires users to actively search for information that is important to them. Another Internet interaction model, the asynchronous model (also called the "push" model), has become increasingly popular. Servers that use the asynchronous model do not wait until a user requests information. Instead, they use a profile to determine which information is important to the user and asynchronously send the information to the user as soon as it becomes available.

The UP.Link platform fully supports the asynchronous model of Internet interaction, allowing HDML services to asynchronously send information to UP.Link subscribers. The asynchronous messages that HDML services send to UP.Link subscribers are called notifications. You can use notifications for tasks such as the following:

• Alerting subscribers of security price changes or fulfillment of securities trades

• Providing subscribers with timely warnings of hazardous weather or traffic conditions

• Updating sports scores that the subscriber is interested in

• Ensuring that obsolete data from your service is removed from an UP.Phone's cache

The rest of this chapter describes how to create HDML services that send notifications. It also provides instructions for testing notifications with the UP.Simulator.

This chapter assumes that you have a basic knowledge of Secure Sockets Layer (SSL), certificates (or Digital IDs), and Certificate Authorities. If you are not familiar with these concepts, you can find background information at Web sites such as the following:

http://home.netscape.com/info/security-doc.html
http://www.verisign.com