I am trying to develop a publish/subscribe system.
To this end, I have read some papers and articles regarding it.
And they all talk about Messaging service as an integral part of publish/subscribe system.
My question is, can I develop a publish subscribe system without using MOM like JMS? Or am I missing or oversimplifying things?
I do not think you are oversimplifying things. There are stand-alone products available that provide advanced functionality based on publish/subscribe, without being part of a larger MOM system.
One of them is a group of products implementing the Data Distribution Service (DDS) specification, as standardized by the Object Management Group (OMG). Check out this Wikipedia entry for a very brief introduction and list of references.
DDS supports many advanced data management features like a strong-typed and content aware databus, distributed state management and historical data access. Its rich set of Quality of Service settings allows to off-load a lot of the complexity from your applications to the middleware. This is all based on the publish/subscribe paradigm.
If you would tell more about your application, then I might be able to point you to similar use cases using this technology -- if you are interested.
It depends what you mean by "MOM". If you think MOM = JMS then yes, there are plenty of pub/sub applications which are not JMS servers (off the top of my head): 0MQ, TIBCO Rendezvous and the many AMQP implementations around.
I guess my definition of MOM is an infrastructure for reliably getting a message from one system to another in an asynchronous manner. Pub/sub is a feature on top of the message transport which allows a message to be distributed to multiple other systems. Once you get beyond the point of opening a socket and stuffing a bunch of bytes down it, I would argue you are in the realm of MOM.
So, no you don't need JMS to do pub/sub....there are plenty of open-source and closed-source alternatives out there. Which one depends on your requirements and skills.
You can look at multicast that provides one to many communication. Multicast does not require MOM, instead it requires multicast enabled IP network. Usually the network routers take care of creating copies of message and delivering messages to destinations.
