B2B Integration : A Practical Guide to Collaborative E-commerce

220 B2B Integration — A Practical Guide to Collaborative E-commerce
The typical MOM system contains the following components:
• Messages;
• Queues — the physical MOM server; and
• Messaging Clients — the sender and receiver.
Messages — Messages generally consist of two parts: a header and a
body. The header contains information to route and identify each message.
The body contains the application data or message content. Messages
can be assigned priorities so that higher priority messages can be
processed before lower priority messages, improving overall system
performance.
Queues — Queues are the mailboxes or inboxes of MOM. Queues
receive and store messages until the receiving applications are ready to
retrieve each message. Queues may be physically located on the sending
computer, the receiving computer, or both.
Queues are managed by a message queue server that is independent
of either the application client or application server. The server may
also manage several queues on one host machine.
Queues may be persistent or non-persistent. Non-persistent queues
store messages in memory, which means that if the message queuing
server fails messages could be lost. Persistent queues will write messages
to a physical disk, ensuring that they can be recovered in the event of a
server failure.
Persistent queues can provide guaranteed delivery of messages.
Guaranteed delivery can be beneficial where the reliability of the
network or applications themselves cannot be guaranteed. Persistent
queues typically require more resources and can be slower than nonpersistent
queues, but are often a necessity in most critical business
applications.
Message Clients — Message clients reside with client applications and
provide an API to allow the application to send and receive messages.
Using the API, an application is able to initiate a session, prepare a
message, set routing parameters and send messages to the intended
queue.