Moving beyond the fourth dimension with an IFC-based single project database

4D CAD has been an active research area for many years. The first generation 4D toots simulated construction schedules and demonstrated the potential benefits in several case studies. Researchers tried to improve the functionality of the first generation 4D tools by adding annotations and highlighting the building elements that have problems. The future generation 4D tools are expected to include more than these. It has been envisioned that 4D models would he part of project databases in order to take decisions related with different project dimensions. This paper presents the development and implementation of a new 4D planning tool which is a part of a product model-based project database. This tool brings the 4D simulation and cost estimation together and aims to contribute to what-if analysis in construction projects. The last part of the paper presents a case study in which the proposed prototype is evaluated. (C) 2004 Elsevier B.V. All rights reserved.