The Apple Push Notification service (APNs) provides feedback to your server that may require specific actions.
For example, if APNs tells you that a push token is invalid, remove that device and its registrations from your server.
It must include the protocol, and it can include an optional port number.
This table includes a last-update tag (such as a time stamp) for when the pass was last updated, and typically includes whatever data you need to generate the actual pass. A registration is a relationship between a device and a pass.
You need to be able to look up information in both directions: to find the passes that a given device has registered for, and to find the devices that have registered for a given pass.
It shows that the request for an update to a pass is coming from the user who has the pass and not from a third party. Your server needs to remember certain information between requests.
There are two entities—devices and passes—and one relationship, registrations.
In this case, you provide only a pass, so Wallet needs a standardized way to communicate with your server.