Open architecture is a design approach based on industry standards to make the modular parts of a computer program easily interchangeable. This deliberate separation of the system into easily replaced parts applies during design, development, and also to the final project. An open approach is used with hardware, software, and communication protocols. Benefits include connectivity, interoperability, expandability, system evolution, integration, and portability. This paper discusses the benefits of open systems and reviews some of the competing standards which apply to computer systems in the water industry. An important caution is included: don't assume you can easily identify what the "standards" really are to produce or specify your "open" system. Open architecture is discussed in terms of operating systems, hardware, and the human interface.