Creating Service Broker Contracts
Contracts define the name of a specific business task and list the message types used in that task. Service Broker contracts define two different service roles: the initiator and the target. The initiator of a conversation begins the conversation by sending a message to the target. The contract that the conversation uses defines which service role can send messages of a given message type.
For each task that the service performs, create a contract that includes the message types for each step in the task. For each message type, specify whether the message type is sent from the initiator to the target, from the target to the initiator, or in both directions.
A contract does not specify message ordering or the number of messages of a particular type that can be sent. Service Broker requires that the initiator send the first message in a dialog conversation. After the first message, there are no ordering requirements.
More than one contract can use the same message types. For example, a message that consists of an XML document that contains a part number and quantity may be useful in a task that accepts an order from a customer, a task that manages inventory, and a task that requests shipping. Each task corresponds to a distinct contract, but all three contracts can use the same message type.
The network format for a message includes the name of the contract. Therefore, contract names are often chosen to avoid collation issues and naming conflicts. For more information on naming, see Naming Service Broker Objects.