If a component should be used in the VEC it must be instantiated. This can be done in two ways. The first way is used if a concrete part number is known. The second way is used if a part number is unknown and only requirements for a component should be defined.
The first case is illustrated in this diagram and is quite similar to the way how components have been used in the KBL. The part is identified by a PartVersion with a PartNumber, Version and the issuing Company. The general properties of the component are defined by a specification (a FixingSpecification in the example). The use of the component is expressed by a “PartOccurrence”. All usage specific properties of component (e.g. the length of a wire) are defined by a Role. The used role must correspond to a specification. The VEC Naming Convention is XXXRole corresponds to XXXSpecification.
In object oriented terms, one can say the PartVersion and Specification are defining the type (or classification) of a component, the PartOccurrence and the Role are defining the instance of a component.