What is the difference between enterprise application integration (EAI) and the enterprise service bus (ESB)?
EAI, by the way, is a term based on my book by the same name written almost 10 years ago now, if you can believe that.
Included in EAI is the notion of service-oriented, information-oriented, process-oriented, etc. Thus, the notion of EAI is really a complete stack, encompassing all types of integration patterns. It's really a concept rather than a class of technology.
In fact, I defined EAI as: "EAI encompasses approaches, methodologies, standards, and technologies allowing very diverse but important systems to share information, processes, and behavior in support of the core business."
I defined the concept of ESBs in the EAI book as what it is: An enabling technology for EAI. EAI is a larger notion, where ESBs are a mere instance of technology. It's almost like saying "Automobiles are better than the concept of transportation."