The key concepts of the VEC are DocumentVersion and 7:PartVersion (see Figure 3).

Figure 3 – Basic Structure of VEC Data

A 7:PartVersion in VEC is a unique identifier for a specific version/revision of a part. In VEC terms, a part is essentially anything that is used in the product or is created during production (a part can be composed of instances of other parts). This means that a 7:PartVersion in VEC applies to both the Part and Article in terms of this Companion Specification.

Note: A Part represents a type definition, not a specific instance of a Part; in other words, a Part is identified by a part or material number, not a serial number.

The term DocumentVersion goes back to the roots of VEC in the STEP standard and the document-oriented product development that prevailed at that time. In fact, DocumentVersion in the VEC stands for any piece of information or a data set that is clearly identifiable and whose changes can be tracked (e.g., a certain state of the properties of a connector, a terminal or a wire [Parts in this Companion Specification], or the definition of a lead set [Article in this Companion Specification]).

The content of a DocmentVersion is used to describe 7:PartVersions. They are represented by individual entities for the following reasons:

1. In general, a document can describe multiple parts at same time, whereas a part can also be described by multiple documents (e.g., a data sheet, a drawing, a 3D model).
2. Both can evolve independently, so tracking of changes & revisions must also be tracked inidividually (e.g., the data for a component can change without changing the physical component).

For example, in the context of this Companion Specification, this could mean that if a machine is sent a new 7:PartVersion, the input material has changed physically and the machine needs to be re-equipped for this new material. However, if only the content of a DocumentVersion changes, the same material processed, just in a different way.

The 7:PartVersion and DocumentVersion is a generic concept for tracking hardware and information changes. The information is described using specific subtypes of Specifications within a DocumentVersion.

Every subset of the VEC model that defines a specific aspect of the product has its own Specification; for example, a connector is described by a ConnectorHousingSpecification, a terminal by TerminalSpecification, etc. The same applies for more complex aspects of the article definition; e.g., the bill of materials is defined with a PartStructureSpecification, the contacting of wire ends with terminals with a ContactingSpecification, the basic structure of a wiring harness or leadset by a TopologySpecification, the geometric form by a BuildingBlockSpecification3D, etc.