Programming Social Applications

The Salmon Protocol Workflow

The Salmon protocol itself simply defines methods for unifying conversations and updated content among a series of sites or services. Its workflow includes two main actors that will be communicating back and forth:

Publisher (source)

The site or services containing the content and conversation entities that other sites subscribe to or aggregate

Subscriber (aggregator)

The sites or services that aggregate the content and conversations from the publisher, syndicating out that content on their own sites

The communication between these two entities spans several different steps, which we’ll cover next.

1. Publisher pushes updated content to subscriber

At the first stage of the process, the publisher updates its content or has updates to its discussion threads. It pushes these updates through to its subscribers via a communication method such as PubSubHubbub so that the subscribers may update their content. Figure 10-12 shows this full flow—from the publisher through the hub to the subscribers.

Figure 10-12. Salmon, step 1: Publisher pushes updated content to subscribers through hub (e.g., PubSubHubbub)

This step mirrors the communication step between publisher and subscriber that we saw in the PubSubHubbub protocol, where a centralized hub controls the flow of updates from publisher to subscriber.

When the content is pushed to the subscriber, it contains a link parameter ...