Basic Administration > Administering Windchill > Contexts – Distributed and Hierarchical Administration > Administering the Versioning of Parts, Documents, and CAD Documents > Understanding the Use of Versioning Schemes > Iteration
  
Iteration
When users select the Check Out action, modify the part or document, and select the Check In action, your Windchill solution creates a new version of the part or document as the next iteration of the current revision upon check in. For example, if the previous version was A.2, the new iteration would be version A.3.