SOURCE MEDIA vs Media type

Vorbis Comments have the 'SOURCE MEDIUM' or 'SOURCEMEDIA' tag (depending on which authority one refers to), while MP3 has the 'Media type' (or 'Mediatype') tag, both of which describe the type of the source media from which this file came (eg. CD), so they correspond to one another.

I wish to add a column to set/view this tag, but since I work with both FLAC and MP3 files, what should the column be named, and how should it be defined (proper spelling, case, with/without space)?

AFAIK if you have a flac field with a different name than the one used generally in MP3tag you may define a mapping in Tools>Option>Tags>Mapping.
There you enter MEDIATYPE as source and the correct name for the flac file as target.
What the correct name is ... I don't know.

Thanks for the feedback. But perhaps the FLAC comment name should be source, and MP3 tag name should be target?

Okay, so I created a column named MediaType, with Value and Field both set to %mediatype%. Next, I mapped VorbisComment SOURCEMEDIA to MEDIATYPE. Is this correct?

Previously, I also created columns for TrackTotal (Value/Field %tracktotal%), DiscNumber (Value/Field %discnumber%), and DiscTotal (Value/Field %disctotal%). Was that correct, and should I also add mappings for these?

So far, all I've been able to find regarding Vorbis comment standards are all quite old:
[1] Ogg Vorbis I format specification: comment field and header specification
Appears to be an official page, only date is: © 1994 - 2005

[2] Field names
Also appears to be an official page, last edited on 18 August 2015

[3] Proposals for extending Ogg Vorbis comments
by David on Sep 28th, 2004

[4] Ogg Vorbis Comment Field Recommendations
by Jonathan Walther, Last updated Thu Jul 3 20:35:53 PDT 2003

The xiph documentation [1] states that field names are to be: "case-insensitive field name that may consist of ASCII 0x20 through 0x7D, 0x3D ('=') excluded." So, ASCII only. This also specifically states that field names may contain spaces (ASCII 0x20). Yet every one of the standard field names on that same page, is without spaces (eg. TRACKNUMBER).

The proposed additions to the standard field names, also from xiph [2] are also without spaces (eg. TRACKTOTAL, DISCNUMBER, DISCTOTAL), and include SOURCEMEDIA, as proposed by Jonathan [4]. But David [3] seems to take exception, proposing 'SOURCE MEDIUM', saying "My final gripe is that the author of the recommendations [referring to Jonathan [4]] seems to have an irrational fear of spaces. Spaces are explicitly allowed in field names and should be used when appropriate instead of creating jumbled messes of letters."

On this I side with the official xiph documentation, as none of their names include spaces. However, I have to agree with David [3] that " The concept of singleton tags, though logical for some fields, drastically limits the flexibility of the comments when applied to AUTHOR."

Apart from those minor issues, both [3] and [4] contain valuable extensions to the very limited standard lists of [1] and [2]. I wonder if we'll ever see an official extended list?