This paper discusses a stmctured data modeling approach which is used to maintain and support two different simulation tools. The data model is stored in a relational database system which provides the links for each tool to access the data. One tool provides short interval production schedules for the semiconductor manufacturing operations at NCR and the other tool performs a wide variety of factory analyses on the same wafer fabrication plants. Powerful user interfaces were built on this system which enable the end users to run simulations of both experimental and actual situations. This environment has also facilitated the maintenance and continuing use of the data over a period of twenty months. In this paper we will review the use of the data model in linking manufacturing users to simulation tools, describe the tools currently in use at NCR and highlight the pros and cons of using multiple tools and a central database.