Overview of Message Draft 4

Just finished draft 4 of REST-* Messaging.  Please check our our discussion group if you want to talk more about it.  Here’s a list of resources and their corresponding relationships for a high level overview.  See the spec for more details.  It relies heavily on Link headers.  The current draft shows a lot of example HTTP request/responses to give you a good idea of what is going on.

Destination

A queue or a topic resource.

Relationships:

• post-message – link to POST/create a message to a queue or topic.  This can be
• post-message-once – link to POST/create a message to a queue or topic using the POST-Once-Exactlly (POE) pattern
• post-batch – POST/create a batch of messages using Atom or Multipart
• post-batch-once – POST/create a batch using the POE pattern.

Message

Every message posted creates a message resource that can be viewed for adminstration, auditing, monitoring, or usage.

Links Relationships:

• reply-to.  Destination that you can reply to
• reply-to-once.  Destination that you can reply to once using the POST-Only-Once pattern
• reply-to-batch. Destination that you can reply with a batch of messages
• reply-to-batch-once.  Batch using POE.
• next.  If pulling from a topic, messages will have this link.  This is the next message after this one.
• acknowledgement.  If pulling from a queue, this link allows you to change the state of the message to acknowleged or not.
• generator, Destination that the message came from

Topic

Has the same links as Destination with these added:

Link Relationships:

• next.  GET the next incoming message.  Clients should use the Accept-Wait header to set a blocking timeout (see later).
• last.  Last posted message to the topic
• first.  First message posted to topic, or, the first message that is still around.
• subscribers. URL that allows you to view (GET) or create/register (POST) a list of URLs to forward messages to.

Queue

Same as Destination, but these additional link relationships:

Link Relationships:

• poller.  Alias to the next available message in the queue.  Returns a message representation along with a Content-Location header pointing to the real one.  a POST is required to access this because the state of the queue is changed.
• subscribers.  Same as topic push model.

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