sentences:  In 1984, RUCAPS was described as a 2½ dimensional interactive system, closer to the philosophy of 2D interactive systems such as ARK/2 or DAISY, and concentrating on the rapid production of 2D drawings (plans, elevations and sections).During the early 1980s, Ingram worked on a supplementary 3D file structure for RUCAPS, where, by running a separate program and with manual intervention, a flat 3D file could be generated, allowing the production of perspectives and images.RUCAPS did carry the 'weather vane' concept from UK-based Applied Research's Building Design System, BDS, now found in most modern BIM systems, but did not have interactive 3D windows or rule-based language - core characteristics of today's BIM applications.