Creo Direct > Using Selection in Creo Direct > About Inferred References
  
About Inferred References
When working with certain commands, you can use inferred references in place of referencing datum axis. Here, instead of creating a reference datum axis, you can select geometry such as edges, curves, cylinders, revolved surfaces, lines, arcs, or circles. This automatically creates an internal datum axis that is associated with the selected geometry.
You can use inferred references with the following commands:
Command
Inferred Reference
Operation
Revolve
Face, Edge, Axis, Sketch Geometry
Reposition origin to specify rotation axis.
Move
Surface, Face, Edge, Axis, Datum, Sketch Geometry
Reposition origin to specify rotation axis
Draft
Surface, Face, Edge, Sketch Geometry
Define the pull direction.
Pattern
Plane, Surface, Face, Edge, Sketch Geometry, Axis
Define a direction for linear pattern or an axis for rotational pattern.