Information about your production asset and its various Assembly representations is stored in an assembly definition (assemblyDefinition node). Assembly definitions let you switch between the different representations of the production asset. A Maya scene can contain only one assemblyDefinition node, so each assembly definition must be as saved as a separate .ma or .mb scene file. (See Create an assembly definition.)
When you create an assemblyDefinition node, it appears in the Outliner, Node Editor, and Hypergraph represented by this icon: 
.
The following image illustrates a typical assembly definition.
Important notes
When using assembly definitions in your scene, consider the following:
- Only one assembly definition can be referenced by an assembly reference node. If your scene contains more than one assembly definition node, an error occurs and nothing is referenced.
- Grouping or parenting assembly definition nodes to other Maya nodes or assembly definition nodes can cause unpredictable results.
- Scene Assembly and Maya File referencing are not compatible.