MOM vs ESB

MOM - Message Oriented Middleware

ESB - Enterprise Service BUS

I consider MOM a building block for ESB solutions. In fact, ESB solutions reach their own loose coupling and asynchronous communication capabilities, just using the paradigm offered by the specific MOM implementation.

Therefore, MOMs represent solutions for data/events distribution at customized level of QoSs (according to the specific vendor implementation), instead ESBs represent solutions providing capabilities to realize complex orchestrations in a SOA scenario (where we have multiple providers offering their services, and multiple consumers interested in consuming the services offered by the first ones).

Complex orchestrations imply communication between legacy systems, everyone of these with its own data domain representation (rules and services on specific data) and its own communication paradigm (one consumer interact with the ESB using CORBA, another one using WS, and so on).

It is clear that ESB represents a more complex architectural solution aimed to provide the abstraction of data-bus (such as the electronic buses that everyone have in his own pc), able to connect a plethora of service providers to a not well specified plethora of service consumers, hiding heterogeneity in (i) data representation and (ii) communication.

ESB is just yet another buzzword, as is SOA 2.0.

You can have a ESB system easily implemented with normal Web Services with a queue behind them. You can have message routing and or orchestration with SOA 1.0 (Tibco{EMS}, BizzTalk), one things does not stop the other really. More importantly, it is the semantics given to the messages exchanged in the system that play an important role, in this case events. Messages as events, are triggers about something that happened in your system, so the context is different.

ESB:

 MOM :