This paper introduces the ORBS expert-system writing environment. In defining ORBS, we have atempted to use the key ideas from past expert system language efforts in building an environment that supports incremental, interactive construction of expert systems. Among others, ORBS inherits ideas from Hearsay III, YAPS, RLL and LOOPS. The paper follows an extended example of the ORBSrepresentation of a VLSI silicon compilation rule.