JBoss Enterprise SOA Platform 4.3 Programmers Guide: A Guide for developers using the JBoss Enterprise SOA Platform 4.3 CP05

An Enterprise Service Bus (ESB) is regarded by many as the next generation of Enterprise Application Integration (EAI) technology. A good Enterprise Service Bus will offer capabilities that mirror those of existing EAI solutions but will not lock you into the offerings of one vendor.
A traditional EAI stack consists of the following:
• Business Process Monitoring
• Integrated Development Environment
• Human Work-flow User Interface
• Business Process Management
• Connectors
• Transaction Manager
• Security
• Application Container
• Messaging Service
• Meta-data Repository
• Naming and Directory Service
• Distributed Computing Architecture
As was the case with the older EAI systems, the Enterprise Service Bus does not deal with business logic; that is left to higher level programs. Rather, it deals with infrastructure logic. Although there are many different definitions of what constitutes an ESB, everyone agrees that they are a fundamental part of any Service-Oriented Architecture (SOA) Platform. However, a SOA is not simply a technology or a product: rather, it is a style of design, many aspects of which (such as the architecture, methodology and organisation) are unrelated to the actual technology. However, obviously at some point in time, it becomes necessary to map the abstract SOA concepts onto a concrete implementation and that is where the ESB "comes into play."