global default musings

[gmabey]

I've been looking at the global properties, and have some questions -- apologies if these have been already beat-to-death in some other forum.

1. I don't think that core:data_type should both be required and have a default value. Could say the same about core:sample_start I guess.
2. Looks like the leading r in core:data_type is now required, whereas it used to be implicit. Was that intentional, or a byproduct of trying to write a regexp that describes the construction of that field?
3. I suppose that core:trailing_bytes doesn't have a default=0 because it's only to be used with NCDs, but why not?
4. I thought that there was an analog to core:trailing_bytes to indicate "skip this number of bytes in the NCD file before reaching the first sample value". I'm thinking of the use case of generating a .sigmf-meta file describing an NCD that is a MIDAS-Blue file, which I'm sure has a header (besides a footer).
5. Did core:sample_rate used to be required? I think I would vote for it to be required.
6. I did once work on a project that had a very slow (geologic) sample rate. Suggest changing core:sample_rate -> "minimum" to 1e-12.

[Teque5]

1. The defaults were created when we thought we were going to read them to insert default values into constructors. I don't think we actually need any of them anymore.
2. I think having c or r first has always been the case.
3. goto 1
4. core:header_bytes
5. Yes it should be required.
6. If you look here it's actually possible to specify x > 0, so we should do that

[gmabey]

1. The defaults were created when we thought we were going to read them to insert default values into constructors. I don't think we actually need any of them anymore.

Do we still want a missing core:num_channels to imply 1? I don't think they hurt anything, and by specifying a default, we allow .sigmf-meta files to be more concise/cleaner when those fields don't apply. However, taking that to an extreme it gets silly, like a default for core:metadata_only of false ...

I have attempted a judicious removal of some of the default lines. Feedback welcome.

3. I think having c or r first has always been the case.

I bet it's from the python code itself that I had that impression.

5. goto 1
6. core:header_bytes

(facepalm)

8. Yes it should be required.
9. If you look here it's actually possible to specify x > 0, so we should do that

Nice.