docs are a bit vague about the naming of the "FDSN:" part and the detail that it can contain multiple colons supposedly

[megies]

1. I find the docs are a bit vague when it comes to what the part in front of the colon should officially be called or referred to as.

Thinking of URI and the docs also mention the URI concept and how it is not immediately specified at the top of the Source Identifier manual/standard, you could assume it would be scheme like it is in the URI realm usually.

At some point in the fine print of the docs, there is this..

The FDSN: portion is a namespace identifier reserved to identify this specification.

.. but

• it's a bit buried in the details section,
• it says ".. is a namespace identifier" as opposed to the crystal clear "a sequence of codes named network, .." used for the other parts at the top of the specs
• and it's not at the top of the specs where all the other parts are clearly named in bold like network code

1b) Furthermore, just reading the docs it's stated that this part is always a fixed string "FDSN:", which implies that having any other string there would mean a "breach" to the standard. Seeing as how libmseed also facilitates reading MSEEDv3 files with something else than "FDSN:" there, I feel like the docs/manual/standard should mention this case and that the intent is probably that third parties could use the same concept in a similar adapted fashion with alternate definition of the part behind the colon.

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2. I just stumbled over this in libmseed source code:

Identifiers may contain additional namespace identifiers, e.g.: "FDSN:AGENCY:NET_STA_LOC_CHAN"

I think this should be at least mentioned in the docs/manual/standard, or maybe even formalized / explicitly spelling out what characters are allowed and if there is a fixed pattern for "agency" also formalizing that?

[crotwell]

Identifiers may contain additional namespace identifiers, e.g.: "FDSN:AGENCY:NET_STA_LOC_CHAN"

I don't think this is valid per the fdsn spec. Maybe it is just a libmseed thing that was leftover from before the fdsn spec was finalized?

My take is that if the source id starts with FDSN: then it must follow the fdsn spec and be
FDSN:net_sta_loc_band_source_subsource. No additional "parts" are allowed.