Subgraph

A collection of base objects can be stored as a subgraph. A subgraph works as a kind of class
or pattern, and in a graph you can create instances of the subgraph, that is subgraph objects.
Stored subgraphs are displayed in the subgraph palette.

You can read about subgraphs in <a href="http://www.proview.se/doc/en_us/man_geref.pdf" target="_blank">man_geref.pdf</a>