Abstract: Tool encapsulation mechanism is the foundation to realize data, control, and process integration of a CAD framework. A new tool encapsulation method is proposed, which, based on client/server middleware, separates encapsulation interface and encapsulation service. It partitions tool encapsulation into two levels: function encapsulation and data encapsulation. Data encapsulation is based on internal semantics of CAD data. Using this method, a distributed framework can “plug and play” heterogeneous tools from different venders , and the tools can take advantage of the high level services provided by the framework.