The mime subtype for a graphic, multimedia object, or piece of supplementary material
The source for this attribute’s values is the Internet Assigned Numbers Authority (IANA 2003).
Although this Tag Set cannot enforce it, the element <graphic> should be limited to still images. The element <media> should be reserved for objects whose @mime-subtype involves video, audio, moving images, time-dependent graphic types, and other non-XML data types. Mimetypes and subtypes should be set accordingly but are not constrained by this Tag Set.