1. A method performed by a CAD data processing system, comprising: receiving an object model in a CAD system, the object model including a plurality of features; creating a blend as part of the object model, using at least one of the features, and removing the used features; creating a construction body corresponding to the object model; storing the removed features in the construction body; wherein the removed features include unders for the blend; modifying at least one of the unders for the blend that is stored in the construction body; creating a modified blend as part of the object model using at least one of the modified unders without recreating, in the object model, the unders for the blend; and performing a CAD operation on the object model using the features stored in the construction body.