ZOG was an early hypertext system developed at Carnegie Mellon University during the 1970s by Donald McCracken and Robert Akscyn. ZOG was first developed by Allen Newell and George Robertson to serve as the front end for AI and Cognitive Science programs brought together at CMU for a summer workshop. The ZOG project was as an outgrowth of long-term artificial intelligence research led by Allen Newell and funded by the Office of Naval Research.
ZOG consisted of frames that contained a title, a description, a line containing ZOG system commands, and selections (menu items) that led to other frames. ZOG pioneered the "frame" or "card" model of hypertext later popularized by HyperCard. In such systems, the frames or cards cannot scroll to show content that is part of the same document but held offscreen. Instead, text that exceeds the capacity of one screen must be placed in another (which then constitutes a separate frame or card).
The ZOG database became fully functional around 1977. Beginning in 1980, ZOG was ported from DEC VAX version (written in an experimental language called "L*") to the Pascal-based Three Rivers PERQ workstation and was used for a shipwide local area network on the American aircraft carrier USS Carl Vinson. In 1981, Rob Akscyn and Donald McCracken, two principals from the ZOG project, founded Knowledge Systems to develop and market a commercial follow-on to ZOG called KMS ("Knowledge Management System").