- PDB("pdb", "xml"), MMCIF("mmcif", "mmcif"), FILE("?", "?");
+ PDB("pdb", "pdb"), MMCIF("mmcif", "cif"), FILE("?", "?");
+
+ /*
+ * file extension for cached structure file; must be one that
+ * is recognised by Chimera 'open' command
+ * @see https://www.cgl.ucsf.edu/chimera/current/docs/UsersGuide/filetypes.html
+ */