We present the implementation of the query function for the Penguin system. Penguin is an object-oriented database system that supports multiple object views on a relational database. It enables many applications to share a database using di erent object schemata. Also, users can take queries for the Penguin database in their applications, to retrieve objects on the heterogeneous data model. The query function is very powerful for manufacturing and engineering purposes, that is, connections between relations and methods de ned by users in applications are available in query requests. We introduce the object model and the query execution algorithm of the Penguin system with an example for a steel plant, and show the system con guration for the implementation of the query function.