Hi Markus,
Great question! Particularly because this is exactly the sort of use case we designed our model around.
if you take a tissue sample of the same tree every year, would the
identifier
in individualID be the same for all of them or be different? WIth the
current
dwc:individualID definition it would be the same for all samples. If I understand you correct each sample would have its own "individual" identifier in your proposal? It can't see how you can collapse these two
things
into one definition.
No, that is not how we would handle it.
In our model, there would be one IndividualID to represent the tree, spanning the time period beginning (more or less) when the seed was germinated, until the time at which the entire physical structure of the tree was disintegrated. It is an individual tree.
There would be multiple Occurrence instances, for each time that someone observed or sampled or otherwise wished to document some condition of that tree. All of these Occurrence instances would refer to the same individualID value (i.e., the "tree"). In the example above, this means there would be a different Occurrence instance for each year that a sample is taken -- because in each case, an assertion that the full tree existed at a certain time and place can be made (I understand that trees tend not to move around very much, so the Location for each event associated with each Occurrence would, in this case, remain the same; but the other Event properties -- such as eventID, samplingProtocol, samplingEffort, eventDate, eventTime, startDayOfYear, endDayOfYear, year, month, day, verbatimEventDate, habitat, fieldNumber, fieldNotes, eventRemarks -- would be documented accordingly for each sampling Occurrence instance).
Suppose that the tree is visited every month, but only sampled once per year. In that case, there would be an Occurrence record for every monthly visit. In other words, an Occurrence instance exists regardless of whether a physical sample was made or not. Any in-situ images made of the tree would likewise be associated with the specific Occurrence instance, and each image would represent a separate instance of "Evidence".
Now, let's focus on the annual samplings. Every time a new sample is taken from the tree, at least one new instance of Individual (with a unique individualID value) is created to represent the sample. This sample (individual instance) may be a "gathering" (set of multiple individual specimens gathered at the same time), or it may be a single specimen, or it may be simply a tissue sample intended for destructive analysis. In any case, it's a new individual instance derived from the "parent" individual instance representing the whole tree. In our implementation, "Individual" can be hierarchical, such that a whole-organism tree can be sub-sampled with many "child" instances of "gatherings" (say, one gathering each year), and each gathering may have multiple child "specimen" individuals (e.g. individual botanical sheets created from the multiple items of a single gathering), and each specimen may have further "child" subsamples extracted for DNA analysis (or whatever), and the hierarchy can continue on down to whatever derivatives that people feel a need to keep track of (e.g., aliquot).
The point is, all Individual instances are well-defined physical objects (or well-defined sets of physical objects), and they can be arranged in a n-tiered hierarchy.
Moreover, each Individual that can be characterized as a "sample" (what we refer to as a "CollectionObject") may also have a property value for "CollectionOccurrenceID" -- which refers to the specific Occurrence instance at which the sample was obtained.
So, for example, if the tree is visited on May 27, 2013 and a specimen (sample) is taken, then: 1) An Event instance is generated to represent the event where the tree was visited; 2) An Occurrence instance is generated, which refers to the new EventID, and the existing IndividualID for the whole tree, and includes whatever other Occurrence properties are relevant for the tree at the time of this Occurrence 3) An Individual instance is generated for the specimen, which has a property value for parentIndividualID that refers to the individualID for the whole tree, and a property value for collectionOccurrenceID that refers the Occurrence instance where the specimen was collected.
So, to summarize the answer to your question: - There are multiple Occurrence instances that refer to the same Individual instance representing the whole tree (and, hence can be collapsed to the same IndividualID value). - Any Individual can have derivatives that are themselves unique Individual instances. - Individuals are arranged hierarchically, and certain properties can be inherited up or down the hierarchy, depending on the properties and their associated logical constraints.
At some point, I will assemble a set of other specific use cases, and how we manage them through our use of the "Individual" instance (although I will probably not use the word "Individual", as this seems to cause too much confusion in these discussions).
Aloha, Rich