Table 3.

Table 3: Metadata elements additionally added to the working document for the SSSOM mapping between DwC and MIxS keys. These metadata elements were additionally added to facilitate the mapping process by having all the information needed as part of one spreadsheet. Please see an example of how these keys were used in the mapping in Suppl. material 1 Section 1.

Element ID	Description	TSV/RDF Example
subject_definition	The definition of the subject of this mapping.	The original description of the depth below the local surface.
subject_valueSyntax	The value syntax expected for the subject of this mapping.	verbatim
syntax_predicate_id	The ID of the predicate or relation that relates the syntax of the subject and object of this match.	skos:relatedMatch
syntax_predicate_label	The label of the predicate/relation of the syntactic mapping.	related match to
object_definition	The definition of the object of this mapping.	Depth is defined as the vertical distance below local surface, e.g., for sediment or soil samples depth is measured from sediment or soil surface, respectively. Depth can be reported as an interval for subsurface samples.
object_valueSyntax	The value syntax expected for the object of this mapping.	{float} {unit}
syntax_comment	Free text field containing either curator notes or text generated by a tool providing additional informative information on the syntactic mapping.	The subject expects a verbatim input (so anything really), while the object expects a {float} {unit} entry.