This part of ISO 14649 specifies the technology specific data elements needed as process data for turning. Together with the general process data described in ISO 14649-10, it describes the interface between a computerized numerical controller and the programming system (i.e. CAM system or shop floor programming system) for turning. It can be used for turning operations on all types of machines including turning machine or lathe, or turning centers. In this version, feature and operation data models for conventional turning, involving only x and z movements, are covered. Features and operations for the composite machining including c-axis operation will be covered in the later version of this document or in a separate document. Also, the scope of this part of ISO 14649 does not include any other technologies, like milling, grinding, contour cutting, or EDM. These technologies will be described in other parts of the ISO 14649 series. The subject of the turning schema, which is described in this document, is the definition of technology specific data types representing machining features and processes for turning operation on lathes. Not included in this schema are representations, executable objects, and base classes which are common for all technologies. They are referenced from ISO 10303’s generic resources and ISO 14649-10. The description of process data is done using the EXPRESS language as defined in ISO 10303-11. The encoding of the data is done using ISO 10303-21.