Revision of Guidelines 3.7. Description of Folia

[riedde]

While the process of introducing structure for extending section 3.7 of the guidelines it was noted that the Description of Folia section should be revised.

See also the conversations at music-encoding/music-encoding#990

• https://github.com/music-encoding/music-encoding/pull/990/files/5c84e0d82a6156b08b89300394a80a57da48c4a0#r977409267
• https://github.com/music-encoding/music-encoding/pull/990/files/5c84e0d82a6156b08b89300394a80a57da48c4a0#r977394685
• https://github.com/music-encoding/music-encoding/pull/990/files#r977381502
• https://github.com/music-encoding/music-encoding/pull/990/files#r977408187

[riedde]

https://github.com/music-encoding/music-encoding/pull/990/files/7d5316d6ca82ddb101b9bd4889421b14c24618ea#r979628425
Request: <signatures> could be added to the documentation of folia desc?

[riedde]

Also see suggestion:

 <p>The values of those attributes, however, specify the height and width of the digital resource, the scan of the source, and they are typically given in pixels (see <ptr target="#facsimileElements"/>). In contrast, <gi scheme="MEI">folium</gi> and <gi scheme="MEI">bifolium</gi> may provide the dimensions of the original source in physical units, such as centimetres or inches. This makes it possible to compare separate parts of a manuscripts stored in different libraries, which may be scanned at different resolutions. In case of <gi scheme="MEI">bifolium</gi> elements, these dimensions apply to the <hi rend="italic">folded</hi> sheet.</p>

Originally posted by @ahankinson in music-encoding/music-encoding#990 (comment)