You use contracts to specify which messages can flow from which endpoints to which queues. Two T-SQL keywords come into play here:
INITIATOR—This service begins a messaging conversion.
TARGET—This service engages in (or accepts) conversions with an initiator.
As described earlier, the sample system is initiated by a stored procedure in
AdventureWorks2012 that sends a message of type
CatalogChangeMessage to a queue in
CatalogChangeMessage is thus sent by a conversation initiator.
The catalog ...