PASO is a personal computer (PC )based scheduling and shop control tool, which offers high levels of flexibility and low cost customization. PASO features a new, flexible kernel/shell architecture based on OLE component technology. Shop control application interface (SCAPI) has been defined to interface shop control applications with the kernel. PASO's structure is based on a central kernel and a set of independent, interchangeable shells. Unlike conventional solutions, the PASO architecture can survive major changes of the manufacturing environment (eg. a complete change in factory organization). The key to this yet unreached flexibility and configurability is the kernel concept to be applied for shop control. The kernel is a collection of basic data structures and services which are common to all or to the majority of applications. The PASO project developed a new component-based kernel/shell architecture for shop floor control software. Different shell components provide different aspects of the functionality of a shop control system (eg a scheduler, a Gantt chart-style user interface or a database interface). Each shell is independent of all others. The Shop Control Kernel co-ordinates the activities of the shells, keeping track of which shells are active and passing messages and data between shells. The Kernel also contains a library of standard shop control objects, representing entities such as work orders, resources and bills of material. Furthermore, it contains a library of functions for creating, deleting, accessing, manipulating and operating on its shop control objects. Shells have access to the Kernel's object library and its function library. By allowing the creation and manipulation of instances of its objects, the Kernel acts as a repository for shop control data, which all shells can share.