This module explains what is middleware and how it interconnects remotely located users, applications, and databases in the modern digital corporations. This is one module of an extensive handbook that systematically discusses how to translate e-business strategies to working solutions by using the latest distributed computing technologies. Chapters of this module discuss the following topics: a) Middleware Principles, Basic Services (RPC, MOM, RDA, Publish/Subscribe) and Distributed Architectures, b) Web Technologies, XML, Semantic Web, and Web Services Concepts, c) Distributed Objects, CORBA, Web Services, SOAP, WSDL, UDDI, J2EE, .NET, d) Enterprise Data and Transaction Management (TP Heavy, TP Lite), and e) Middleware State of the Practice (Case Studies), Market (Commercial Products), and Art (Research and Development Trends). Chapters also include several real life examples and case studies to highlight practical applications. Additional information and instructor material avaialble from author website (www.amjadumar.com).