Notification Overview
— a high-level view of the notification process
Content within a channel is contained in notifications. The distribution of these notifications is at the heart of a publish/subscribe model of content distribution.
Essentially, the notification process entails two procedures:
- A publisher assigns a value to a channel's attribute.
- A subscriber retrieves the value of a channel's attribute.
Publishers assign values to a channel's attributes by invoking the notify method or function of a proxy. The proxy establishes and maintains connection to a channel, and validates the publisher's notification against the data type for the attributes.
Subscribers retrieve content in much the same way that publishers create it: they initialize a proxy for the channel and invoke an attribute retrieval process to receive notifications for the subjects within the channel for which they are authorized.
Publishers and subscribers have no direct relationship to one another. Rather, each establishes a proxy connection to a channel and its subjects.
For each subscriber, subjects are captured in a subscription or set of subscriptions. The subscription exists for a given subscriber for a particular subject within a channel.
The successful distribution of content ultimately depends on a callback function, in which the application returns data based on the subscription.
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