Message Channels

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Administration Client > Message Channels

The Message Channels administrator is a component within Presence which allows administrators to manage message channels and subscriptions for the Broadcast Messages Task Element.

Understanding Message Channels

Message Channels are organized into a tree-like structure. This means that any given Channel may have one parent Channel and zero or more child Channels.

Here is an example of some Channels:

  • Food
    • Fruit
      • Apples
      • Bananas

Since the "Apples" Channel is a child of the "Fruit" channel, any messages broadcast to the "Apples" Channel will also be sent to subscribers of the "Fruit", and "Food" Channels (since "Fruit" is also a child of "Food").

As a general rule, messages are sent to the Channel that they are originally broadcast to, and are also propagated to the root of the tree. Imagine the following scenarios:

Scenario A

  1. User "Bob" is interested in apples, so he subscribes to the Apples channel.
  2. User "Alice" is interested in all types of fruit, so she subscribes to the "Fruit" channel.
  3. User "Frank" writes an article about Granny Smith apples. He broadcasts this to the "Apples" channel.
  4. Both Alice and Bob receive the article.

Scenario B

  1. Frank then writes a report about banana sales in eastern Europe. He broadcasts this to the "Bananas" channel.
  2. Only Alice receives this report.
  3. Alice and Bob could then apply further restrictions on the content that they receive. For instance Alice could opt to only receive messages where the subject contains the word "report".

Security considerations

Imagine that Frank's report on banana sales is classified, and he doesn't really want Alice to be able to receive it. He could add a child Channel to Bananas like this:

  • Food
    • Fruit
      • Apples
      • Bananas
        • Secret Banana Sales Reports

When creating the Channel, Frank can elect to make the Channel secure - this means that nobody can subscribe to that channel without Frank's permission. If Alice or Bob try to subscribe to this Channel, they will have to wait until Frank authorises the request. We'll discuss this in more details later. When a secure Channel has children, those children will not be accessible to anyone who has not been authorized to subscribe to the secure parent. Similarly, messages are not propagated to the tree root if a channel is secure - they stop at the secure channel. The following example demonstrates how this works:

  • Food
    • Fruit
      • Apples
      • Bananas
        • Secret Banana Sales Reports (Secure)
          • Europe
          • North America
          • Africa
          • Asia Pacific

So, if a message is broadcast to the "Europe" child of "Secret Banana Sales Reports", subscribers to the "Bananas" Channel will not receive it. Subscribers to "Secret Banana Sales Reports" will, and people may only subscribe to the "Europe" Channel if they have already subscribed to the "Secret Banana Sales Reports" Channel.

Requesting permission

Permission to subscribe to a Message Channel is requested through the Channel Subscription web interface. Clicking the "apply for subscription" link next to a secure channel creates a subscription request.

This then automatically alerts any users who are a) running the channel manager application and b) authorized as an administrator for that channel (see Channel Manager documentation for more on this). When authorization is granted, an email is sent to the user. Similarly, if the request is denied, an email will also be sent.

Architecture > Administration Client > Message Channels

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