Have default set of functions that SHOULD be supported as default built-in functions (based on GREL)

[bjdmeest]

• have a subset of functions
• have consistent FnO descriptions
• have large coverage test cases
• update spec to include the SHOULD

[dachafra]

I marked this as working-group as I think it's a good to have.

[dachafra]

Maybe we can include here not only GREL, but also get some inspiration from #30, as the idea is the same, I'll close the other issue and leave this open

[bjdmeest]

Sure, but requiring a SPARQL function engine in a mapping engine (if I understand #30 correctly) is maybe a bit of a large ask for a SHOULD? I don't see any issue having a single FnO function that does SPARQL functions, but I wouldn't like to implement that myself 😅

[bjdmeest]

I made a suggestion of a default set at https://docs.google.com/spreadsheets/d/1mV3gdvcqwPQNAqPq20cGrKS-5DE0jXGtTjO8eACpEiA/edit?gid=0#gid=0