Single source of truth for lyric line IDs

[rpatters1]

By my reading of the reference pages, there is no single source of truth by which to validate a lyric line ID. It seems as though

• any event may have any sequence of lyric IDs, provided they are document-unique
• the global.lyrics.lineMetadata may or may not include every ID used in events.
• the global.lyrics.lineOrder may or may not include the ID s in line metadata and/or events.

I am wondering if it would be a good idea to designate a the source of truth for lyric line IDs. (Perhaps lineOrder or lineMetadata.) Under this proposal, events could only use IDs from the source-of-truth list.

FWIW, the in-progress version of my mnxvalidate utility validates them as follows:

• if both lineOrder and lineMetadata are present, then they must specify an identical set of IDs and event lyric IDs must be in the set.
• if either is present but not both, then the one that is present becomes the list of valid IDs.
• if neither is present, the event IDs are not validated.