: For other meanings, see ACIS (disambiguation)
ACIS stands for Alan, Charles, Ian s System. It is a solid modelling geometric modeling kernel that several CAD packages now use. ACIS uses a sophisticated object-oriented approach for modelling, the data is stored in boundary representation. ACIS is owned by Spatial Technology. This was the author s second generation system, the first generation being Romulus. In 1999 around the time when Spatial was bought out by Dassault Systemes, the file format changed slightly and was no longer openly published.