Product Modeler's Basic Concepts

The product objects are based on the instance-reference mechanism.

This page discusses:

Reference-Instance Mechanism

Purpose
The purpose of the instance-reference mechanism is to segregate the modified versions of content from the original version.

To be used in an assembly, an object requires:

  • One reference: The object data in their initial form (a definition).
  • One or several instances: The object entity customized for a specific context (for example, a product).

Reference-Instance Inheritance
The reference content is the original or primary content that can be replicated in one or more instances. If the reference content is modified, every instance of that content is updated accordingly.

However, changes to the instance do not affect the reference content.

Content inheritance (from reference to instance) is maintained until there is a change of an attribute in the instance content. Modifying an instance attribute stops the automatic update from the reference to the instance.

Reference, Instance, and Occurrence

  • A reference is a definition.
  • Instance: the object specifying the aggregation relationship with the reference
  • Occurrence: the object representing the path of an instance in its context (for example, an assembly). In session, occurrences are displayed. They represent instances in their context.

Example with a product: In a skateboard model, the 4 wheels are occurrences of 2 instances:

  • Two occurrences of one instance that is assembled on the front truck
  • Two occurrences of one instance that is assembled on the rear truck


UI Display

In the tree, a single node is displayed for the instance and its reference. To display the instance or reference attributes, select this node and open the Properties dialog box.