How does a selector work?
In Pub/Sub a selector is like a filter: if a message doesn’t match a subscribers selector, that message will not exist as far as that subscriber is concerned. It will be as if the message was received by the topic before the subscriber connected. In P2P a selector merely limits which message a particular receiver can see, i.e. it is a view applied by the receiver. A receiver can get messages, which did not match another receivers selector.
