This package from freedesktop.org's includes the standard MIME-type XML description files and the update-mime-database command. It is often provided in a Puppy's devx devx sfs. This provides a standard for MIME-types in Linux. HowToAddMIMEType How To Add MIME Type tells you how this works in Puppy.

Install devx devx sfs or appropriate package:-

HowToAddMIMEType How To Add MIME Type

AssociateFiles - How Associate filetypes

InternetMediaTypes Internet Media Types