@User: Mitch gave a good description of it. The only things I would add is that "maglef" files are created by reading a LEF file into magic and writing out a file in magic's own database format. The main advantage of doing this is to toss in additional information that is not available in the LEF format, such as the ordering of pins (to match a SPICE or CDL netlist), and the location of the GDS data. The best reason to use abstract views is to simplify large sections of the layout if they are already completed, verified, and known good, so you don't have to have the detail inside the cell slowing the tool down during viewing, extraction, GDS generation, etc. The downside is that you have to be absolutely sure that the cell represented by the abstract view is known good, because it's easy to hide all sorts of errors behind the abstraction. Also you have to make sure that it points to a valid GDS file, or else swap it out for a non-abstract view before you write GDS. Swapping views between abstract and full layouts can be done by manipulating the search path for cells, and then doing a "load <cell> -dereference" to ignore all the file path bindings for each cell and go find all the cells from the search paths.