# Initial proposed error semantics

* Errors will propagate through piped streams until an error handling stream is encountered
* An error handling stream can be created by using mapError, flatMapError or passing another parameter to ps.through which contains an error handler.
* A stream is "consumed" if its converted to a promise by awaiting its end event, or if its otherwise subscribed to.
* If an error propagates to a consumed stream, it will 
  * reject that stream's promise
  * cancel all subscriptions backwards, such that if a subscription count drops to zero that stream also unsubscribes backwards.