This is a core question that we need to ask when we talk about SOA (Service oriented architecture). SOA connects enterprise components within and outside by easy integration, coordination and loosely coupled processes that can be coupled easily. The main theme that comes up when the number of interacting components increases is the complex messaging and data exchange need. So, now you know what the backbone of SOA is – The messaging system. There are varieties of such messaging systems that are in use today, some which are core Java based and some of them are proprietary – such as IBM MQ.