It's not clear which rules are mandatory and which are "nice to have"

[RoryMMMM]

Thanks for making the effort to publish an API to check files for various conventions. I'm busy trying to wrangle a bunch of files from various oceanographic sensors into a single standardised format. CF-Conventions seems like a good choice but I have little experience with this.

I'm using the MCC tool to validate that my metadata and formats are "good enough" but it's not clear which of the tests are warnings and which are required.

For example:
I pass a netcdf file I've generated from a sensor file and get 482/491 passed and the errors I get seem to be non-issues:

• The variable time failed because the datatype is int64 (This is not the case, probably a bug in the tester)
• It fails on two field names that have dashes in them, I could probably change that without problems
• It complains about a couple variables that don't have standard_names (in this case there aren't existing standard names that cover those variables)
• Also the same for some units not being recognized by UDUNITS.
  I'm sure I'll get other warnings/errors for other files and sensors that I process so let's not focus too much on the above.

In short how do I use this API to tell whether my file is good enough? Should I be aiming for 100% tests passing?

[tloubrieu-jpl]

Thanks @RoryMMMM for reporting that, I am assigning your request to our I&A team.

[edshred2000]

Hi Rory,

I am one of the original developers of MMC tool. It has been around for a while but there are still some nuances to interpreting the output and bugs which you have found.

First I would say passing 482/491 tests is quite good! There was never an expectation to be at 100%.

• The time datatype bug sounds reasonable and I think I have seen that before. Ignore
• Dashes are special chars and not a good idea to put in variable name. Use underscores.
• Often there are variables names that have no associated CF standand_name so dont worry about those. But dont make up a standard_name if it doesnt exisit. Its a carefully curated list by the CF community. You can propose new ones.
• Try to fit into UDUNITs as best you can. But you can safely ignore the errors if you have a "custom" unit. Just make sure its understandable by your community. Dont leave units="" or units="1" if they dont exist, e.g., dimensionless units. Just leave out the unit attribute in that case.

Regards, Ed Armstrong