[tdwg-content] Proposed new Darwin Core terms - abundance, abundanceAsPercent

[John Wieczorek]

I see several problems with using MeasurementOrFact in this way.

What happens when someone wants to add the next MeasurementOrFact to
"Simple" Darwin Core? They won't be able to. "Every field in the
Simple Darwin Core may appear either once or not at all in a single
record - otherwise how could you distinguish one scientificName field
from another one? Think of a database table. It will not allow you to
have the same name for two different fields. Because of this design
restriction (lack of flexibility for the sake of simplicity), the
auxiliary fields from the ResourceRelationship and MeasurementOrFact
classes are of somewhat limited utility here - you could only share
one MeasurementOrFact and one ResourceRelationship per record." [2].

Why should abundance take precedence over any other potential MeasurementOrFact?

Unlike all other terms in Simple Darwin Core, the labels for the
MeasurementOrFact terms will not explicitly state what is in them.
There will be no definition to look up in Darwin Core to understand
that the content is supposed to be an abundance, or what an abundance
is.

With MeasurementOrFact in the Darwin Core Occurrence Core Type [3],
data publishers using Darwin Core Archives would be tempted to use the
terms to capture the measurement or fact from of most importance to
them from their data set, and there would be no guidance to tell them
not to do so. A consumer would have to look into the content of the
measurementType field to understand what to do with the contents of
the other two fields. I'd urge to keep such a mess out of the realm of
Simple Darwin Core.

On Thu, Oct 24, 2013 at 1:30 PM, Éamonn Ó Tuama [GBIF] <eotuama at gbif.org> wrote:
> Following all the excellent contributions on this list relating to
> expressing abundance data in Darwin Core, I think we may have uncovered a
> way that does not require any changes to the DwC standard. As has been
> pointed out, modelling sampling and abundance can be quite complex and
> challenging and is best done as an ontology (as in the work of the BCO).
> >From the GBIF perspective, our goal is to make it as simple as possible for
> data providers to deliver abundance data (in Darwin Core Archive format)
> that can support the science for processes such as CBD and IPBES. Here, I am
> using the term abundance (specifically population abundance) in the sense
> defined by GEO BON: "Quantity of individuals or biomass of a given taxon or
> functional group at a given location" [1].
>
> The challenge is to come up with a way for Simple Darwin Core to express
> abundance data. It looks like we can probably work within the restrictions
> imposed by Simple Darwin Core [2] and use properties from MeasurementOrFact
> because, for the use case in question here, we only need to share one
> MeasurementOrFact per record.
>
> The model: A sample, associated with a sampling protocol has one or more
> taxon occurrence records each of which has an abundance measure which is
> expressed using MeasurementOrFact.
>
> At a minimum, we would need the following three MeasurementOrFact properties
> listed below (with definition and examples):
>
> measurementType
> The nature of the measurement, fact, characteristic, or assertion.
> Examples: "tail length", "temperature", "trap line length", "survey area",
> "trap type".
>
> For abundances we would use: count, percentage
>
> measurementValue
> The value of the measurement, fact, characteristic, or assertion.
> Examples: "45", "20", "1", "14.5", "UV-light".
>
> For abundances we would use any numeric value.
>
> measurementMethod
> A description of or reference to (publication, URI) the method or protocol
> used to determine the measurement, fact, characteristic, or assertion.
> Examples: "minimum convex polygon around burrow entrances" for a home range
> area, "barometric altimeter" for an elevation.
>
> For abundances we would use: Count/sq metre, count/litre, % of biovolume, %
> of species, ...
>
> To enable automated processing, we would need to develop a controlled list
> for measurementMethod and, ideally, there would also be a URI for the
> sampling protocol used which would be recorded in the dwc:samplingProtocol
> field.
>
[1] http://www.earthobservations.org/documents/meetings/201202_geobon_ebv/30_ebv_species_table_v2.pdf
[2] http://rs.tdwg.org/dwc/terms/simple/index.htm#rules
[3] http://rs.gbif.org/core/dwc_occurrence.xml