Subscription Event Protocol

The CloudOS Subscription Event Protocol provides an event based model for managing subscriptions between Personal Clouds. The current implementation of the protocol will create a symmetric relationship between both Personal Clouds. Cloud subscriptions are done in such a way that both the originating and target clouds end up with a unique event channel to the other that is specific to the purpose for the subscription. 

Rulesets do not manage subscriptions directly, but rather rely on the CloudOS service to do it for them. Consequently, to use the Subscription Event Protocol the CloudOS service ruleset must be installed in the Personal Cloud for both the originator and target. The CloudOS service listens for certain events, manages subscriptions, and provides functions for getting information about subscriptions. 

Events

Subscribe

The system:subscribe event is used to create a channel between two Personal Clouds.

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• The channelName attribute is a label associated with the subscription that should convey meaning to developer. The channelName is only used as a component in the creation of the event channel identifier. If no channelName is specified the value of "orphan" will be used.
• The namespace attribute is provided as a means for the developer to group subscriptions within a single, or group, or applications. The namespace is used to filter the list of subscriptions returned by the subscriptionList() function. If no namespace is specified the value of "shared" will be used.
• The relationship attribute allows the developer to characterize the relationship between the originator and target clouds. The relationship attribute should be specified as a pair of values separated by a dash (e.g. parent-child, peer-peer, master-slave). The first value of the relationship attribute will be stored with the originating Personal Cloud subscription, the second value will be stored with the target Personal Cloud subscription. The relationship attribute values are used to filter the list of subscriptions returned by the subscriptionList() function. If no relationship is specified the value of "peer-peer" will be used.
• The targetChannel attribute is the event channel identifier (ECI) for the target cloud to which the subscription is to be made. Usually, this is the well-known ECI (doorbell) for the target cloud. The well-known ECI provides a means for bootstrapping subscriptions between clouds. 

fired {
  raise cloudos event subscribe
    with channelName   = "Coworkers Bob+Ted"
    and  namespace     = "MyFriends"
    and  relationship  = "friend-friend"
    and  targetChannel = "3f15b820-af7ffa7f-012f-4c6e-00163ebczzzz00163ebccdcd"
    and  _api = "sky";
}

cloudos:subscriptionRequestAdded(targetChannel, backChannel, namespace, relationship, channelName)

rule 

process_subscriptionRequestAdded {
  select when cloudos subscriptionRequestAdded
    namespace re/MyFriends/"
    channelName re/Coworkers Bob+Ted/
    relationship re/friend-friend/
  ...
}

cloudos:subscriptionRequestPending(eventChannel, namespace, relationship, channelName)

Subscription Approval or Rejection

Approval

cloudos:subscriptionRequestApproved(eventChannel)

fired {
  raise cloudos event subscriptionRequestApproved
    with eventChannel = "3f15b820-af7f-012f-4c6e-00163ebcaaaa"
    and  _api = "sky";
}

cloudos:CloudOS_subscriptionAdded(eventChannel, backChannel, namespace, relationship, channelName)

rule receiveprocess_subscriptionRequestAdded {
  select when cloudos subscriptionRequestAdded
    namespace re/MyFriends/
    channelName re/Coworkers Bob+Ted/
    relationship re/friend-friend/

  ...
}

fired {
  raise cloudos event subscriptionRequestRejected
    with eventChannel = "3f15b820-af7f-012f-4c6e-00163ebcaaaa"
    and  _api = "sky";
}

rule receive_subscriptionRejected
  select when cloudos subscriptionRejected
    namespace re/MyFriends/
    channelName re/Coworkers Bob+Ted/
    relationship re/friend-friend/

rule receive_subscriptionRejected
  select when cloudos subscriptionRejected
    namespace re/MyFriends/
    channelName re/Coworkers Bob+Ted/
    relationship re/friend-friend/

...

rule receive_CloudOS_subscriptionRemoved
  select when cloudos CloudOS_subscriptionRemoved
    namespace re/MyFriends/
    channelName re/Coworkers Bob+Ted/
    relationship re/friend-friend/

Functions

subscriptionList(namespace, relationship)

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