source_configuration_optional

element_name	kind	external_table	description
source_id	varchar	source_configuration:source_id	Link to source for which this entry corresponds
kind	int	kind:kind	Enumerated data type (numeric, int, etc)
field	varchar	source_configuration_fields:field_id	Field that this entry corresponds to
value	varchar		Kind inherited from field
comments	varchar		Any additional comments.