add temporal extent property for sample description

[smrgeoinfo]

See proposal at https://github.com/isamplesorg/metadata/blob/temporalExtent/notes/temporalExtentProposal.md

we want a way to document time intervals that are important for the context of a material sample.

[ekansa]

Hi @smrgeoinfo looks pretty good:

https://perio.do/technical-overview/

We should explicitly allow a definition (with a concept ID) for different types of events.

• Birth
• Move
• Death
• Formation
• Usage
• etc...

I think the start and end intervals are fine. Some people like to have some more complexity to model the beginning and end of time intervals. A slightly more complex model can be:

• begin of the beginning
• end of the beginning
• being of the end
• end of the end

This 4 coordinate approach is useful to model (for instance) that there may be much more certainty in the end of a time interval than the beginning.

Anyway, for iSamples purposes of general discoverability, I think simple is good. The minimum core time attributes I see are:

• start time (number)
• end time (number)
• event_type (formation, death, date of expedition, date of curation, etc.)