© 2002 by British Computer Society
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A Thread of HOL Development
1 University of Cambridge Computer Laboratory, William Gates Building, J. J. Thomson Ave, Cambridge CB3 0FD, UK Email: mn200@cl.cam.ac.uk
The HOL system is a mechanized proof assistant for higher-order logic that has been under continuous development since the mid-1980s, by an ever-changing group of developers and external contributors. We give a brief overview of various implementations of the HOL logic before focusing on the evolution of certain important features available in a recent implementation. We also illustrate how the module system of Standard ML provided security and modularity in the construction of the HOL kernel, as well as serving in a separate capacity as a useful representation medium for persistent, hierarchical logical theories.