Body tags of connected parts and if the body tag is an occurrence then ask for its part occurrence tag to read the attributes on the connected parts. The body tags are stored in a linear array in blocks of "num_tags_in_set". That is body tags of first set starts at 0 to (num_tags_in_set[0]-1) and for second set it starts from (num_tags_in_set[0]) to (num_tags_in_set[1]-1) and so on for "num_sets".