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A subscription represents a relationship between two picos. It has a name and two channels, one from each pico participating in the subscription to the other. Each side in the subscription can be given a role to further identify the purpose of the subscription. 

In this diagram, from the perspective of pico A, the top channel is the one on which it receives incoming events and queries, so A knows this channel as Rx, and the bottom channel is the one on which pico A transmits events and queries to pico B, so A knows this channel as Tx. Conversely, pico B knows the top channel as Tx and the bottom channel as Rx. Each pico has its own perspective on the subscription.

Subscriptions may also include a role for each pico. From the perspective of pico A, its role in the subscription is known as Rx_role while pico A knows the role of pico B as Tx_role. On the other hand, from pico B's perspective, the role of pico A is Tx_role and its own role is Rx_role. Putting yourself in a pico's place, you can think of Rx_role as my role and Tx_role as the other's role.

Managing Subscriptions Programmatically

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