It is clearly simplest if a file containing zone-to-group mappings has an extension .Z2G to indicate its function and if a Z2G filename is given (e.g. on a command line) without an extension .Z2G will be added automatically. However, for example, a namelist parameter record “FILZ2G = ‘my_z2g_file.dat’” is perfectly acceptable. And “FILZ2G = ‘my_z2g_file’” would have .Z2G added,
A .Z2S file may be defined by the parameter FILZ2S in a matrix .dat file (see 10.5.2) as may a Z2G file via FILZ2G so that these filenames are then embedded within the .UFM files and need not be redefined when needed. All other files, however, would need to be user-set when and as required.
As a matter of good practice and common sense, it is proposed – although this is not a rigid requirement in SATURN – that all Z2G etc. files should (a) have the same “root” filename and (b) be stored in the same folder. In other words, files such as mapping.z2g, mapping.z2s, mapping.g2s, etc. would all be stored in the same folder and therefore have a common root pathname as well as a common filename. The advantage of this is that the user need not define all the possible mapping files since a SATURN program could logically infer a file/path name when necessary.
In particular this facility is routinely used with text descriptor files of the form .G2T whereby if the predicted file mapping.g2t can be found it is used to add text names to groups; if not group text names are simply ignored.