Enterprise integration patterns (EIP) is a catalog of design patterns for developing systems to integrate new and existing software in a business environment. The book, whose full title is Enterprise Integration Patterns: Designing, Building, and Deploying Messaging Solutions, was written by Gregor Hohpe and Bobby Woolf and published in 2003. EIP provides 65 design patterns and includes an icon-based pattern language sometimes called GregorGrams.
A design pattern is a general solution to a design problem that recurs repeatedly in many projects. A pattern describes the problem and its proposed solution and discuss any other important factors. EIP focuses on messaging patterns for enterprise application integration (EAI). Messaging makes it easier for programs to communicate across different programming environments (languages, compilers, and operating systems) because the only thing that each environment needs to understand is the common messaging format and protocol.
Messaging patterns define the means by which different elements in a message-passing system connect and communicate to enable interaction among objects within programs and among various types of software -- which may be written in different languages and exist on different platforms in multiple locations.
See an introductory tutorial on common patterns for enterprise application integration (EAI):