When merging several versions of structural/mechanical data (whether model-based or drawing based) into ARCHICAD, you can place each subsequent version onto its own layer, and save them as separate views. Next, you can open one view, then use the Trace & Reference function to display another view – representing the other variant – alongside or on top of the first one. The program does not recognize the changes automatically, but you can use the Trace functions to identify changes visually in the Floor Plan, Section/Elevation/Interior Elevation, 3D Document, Worksheet, Detail or Layout windows. Next, you can carry out the needed changes manually in the ARCHICAD model.
For details on the Trace & Reference function, see Virtual Trace: Using References to Edit and Compare Model Views and Drawings.