The polyname field is used for multiple tasks and file name extensions are appended depending upon the task. The current boundary mark up can be saved to the polyname (with no extension). Individual mark up files can be loaded and the boundary will be displayed in the specified Tv with the selected display options. Results of model building are stored to the files filename.mml and filename.pca. These are automatically written when the model is built (see below). Construction of the model requires a list of markups. This list is held in simple asci format in the file specified by filename.blt.