Vanguard is a discontinued experimental microkernel developed at Apple Computer, in the research-oriented Apple Advanced Technology Group (ATG) in the early 1990s. Based on the V-System, Vanguard introduced standardized object identifiers and a unique message chaining system for improved performance. Vanguard was not used in any of Apple's commercial products. Development ended in 1993 when Ross Finlayson, the project's main investigator, left Apple.