Since software development is a process of model transformations, to view various models in an integrated manner is a necessity. The purpose of this paper is to propose a new design method incorporating the required organization model (ROM) and IDEF1X data model. For function analysis, requirement specifications are first clustered into object domains using ROM. For data analysis, the IDEF1X is then employed to describe the static structure, which is transformed into a relation schema. Finally, the database system is implemented using an object-oriented (OO) database program. The correspondence and transformation rules of individual models are highlighted. The procedure applying ROM/IDEF1X methodology is demonstrated by a tool database system.