Cognitive Work Analysis (CWA) is a methodology for analyzing complex socio-technical systems. It aims to structure system information in a manner that is meaningful for human control and interaction. The Abstraction Decomposition Space (ADS) in an important tool used during the first phase of CWA to describe the work domain. In this paper we create an ADS for a Semiconductor Fabrication Plant (Fab). This is a High Volume Manufacturing environment and its complexity necessitates a number of adjustments to the original ADS technique. The physical decomposition of the system is de-emphasized and a number of alternative decomposition hierarchies are used instead. The analysis aims to produce artifacts that can aid in the design of decision support systems. These artifacts not only help to assess the information needs of workers, but also structure the work domain in a manner that will inform display design.