[Crm-sig] 6.2.2's MonetaryAmount and Currency

Robert Sanderson RSanderson at getty.edu
Wed Jan 4 01:01:24 EET 2017

Dear all,

At the Getty, we are currently remodeling our Provenance Index data into Linked Open Data.  As you might expect, there is a lot of historical payment information related to the transfer of ownership of objects.  We were very happy to see that 6.2.2 adds in some of the foundational modeling for supporting this information.  The scope notes in the current draft are a little unclear for Monetary_Amount and Currency, however.

We are assuming that the Amount the face value of the money (e.g. $100 USD is always the amount 100 of the currency USD) regardless of the actual _value_ of that amount. If this is correct, then could the scope notes confirm this?  

All currency amounts have an absolute value that changes constantly due to inflation and markets, and there’s no way to associate a date with the amount instance to capture this.  This seems somewhat in conflict with being a subclass of Dimension, which is “the true quantity, independent from its numerical approximation, e.g. in inches or in cm.” – in other words the absolute value, independent of the unit, which is in this case the currency.  As a thought experiment, if the unit of an “inch” were to change definition to be exactly 2.5 centimeters, then I believe from the description of Dimension, that the lengths would remain the same in absolute value, and we would need a new unit for “new inches”.  This is not practical for currency, as we would need new units constantly … which is also forbidden by the scope notes of currency: “One monetary system has only one currency”.  So how are we to deal with comparisons over time?

And in either case, it would be correct to have all uses of $100 USD refer to the exact same resource… there need only be one Monetary_Amount that has a particular value and currency … $100 is $100, regardless.  The practical implication is that Monetary_Amount URIs could be constructed algorithmically along the lines of http://example.org/Monetary_Amount/dollars/100.  This doesn’t seem to be affected by face value vs actual value, but confirmation would be appreciated.

Secondly, and this is likely out of scope for the CRM at this stage, we have a requirement to model where the money comes from and goes to.  For example, there are many occurrences of dealers owning only a part share of an expensive artwork, and the payment being divided according to that share amongst the owning dealers.  For this we need more than just a Monetary_Amount associated with a Purchase, and have been using a new subclass of Activity a “Payment” with properties mirroring transfer of ownership:  paid_amount, paid_to and paid_from.

  "@id": "http://data.getty.edu/museum/Purchase/1", 
  "@type": "crm:E96_Purchase", 
  // …
  "crm:P9_consists_of": {
    "@id": "http://data.getty.edu/museum/Payment/2", 
    "@type": "pi:Payment", 
    "pi:paid_amount": {
      "@id": "http://data.getty.edu/museum/MonetaryAmount/3", 
      "@type": "crm:E97_Monetary_Amount", 
      "rdf:value": 100
    "pi:paid_to": {
      "@id": "http://data.getty.edu/museum/Person/seller", 
      "@type": "crm:E21_Person"
    "pi:paid_from": {
      "@id": "http://data.getty.edu/museum/Person/buyer", 
      "@type": "crm:E21_Person"

This also lets us record, for example, if multiple currencies were used in the transaction (e.g. the price listed was in dollars, but the sale occurred in France and the currency exchanged was francs)

Thoughts on these issues would be greatly appreciated.

Many thanks, and a happy new year to all!

Rob Sanderson
Semantic Architect
J. Paul Getty Trust

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