This mainly discusses the next generation factory automation systems, i.e., open systems. Along the dimension of open architecture, it discusses some standardized methodologies involving Linux open source operating systems, platform independent programming languages, systematic object-oriented software engineering, web-based information publishing, virtual instrument-based system structure, distributed and embedded real-time systems, etc., and their applications in factory automation systems. The resulting open systems are capable of keeping up with the evolving requirements in the factory automation arena, and it is expected that the strict use of standards would bring benefits to enterprises in the long sight.