Thursday, October 4, 2018

Linking uncertain mints to probable matches in Nomisma

We have formalized a new extension to the data model to link identifiable mints whose geographic location is uncertain to the Nomisma URI for the place most likely to have been the production site for the mint. Usually, when a mint is unknown, we simply assign the URI to the nmo:hasMint property in the Nomisma ontology, but several type corpora do contain lists of distinct "uncertain" mints. For example, the Republican mints of Sicily 1 and Sicily 2 have been attributed by Michael Crawford in Roman Republican Coinage (1974).

With the publication of Seleucid Coins Online last December and the impending publication of Ptolemaic Coins Online this fall, we have already or will have created more than 100 additional "uncertain" mints. In many cases, we can use skos:broader to link to a parent region, as the region is usually known to a reasonably high degree of certainty. In some cases, the place can be attributed as "probable", and for research and visualization purposes, it is useful to be able to capture this relationship.

Since skos:related has not been used in Nomisma to link loosely related concepts internally, we have adopted this property to generate a blank node that carries two further properties: the rdf:value that is the URI of the mint and an un:hasUncertainty of nm:uncertain_value, which is used rather generally throughout Nomisma RDF. In theory, we can expand the number of instances of un:Uncertainty to handle various gradations of certainty/uncertainty.

nm:uncertain_52_sco a nmo:Mint,
        skos:Concept ;
    dcterms:isPartOf nm:greek_numismatics ;
    dcterms:source nm:seleucid_coins_online ;
    skos:broader nm:mesopotamia ;
    skos:changeNote <> ;
    skos:definition "Uncertain Mint 52, perhaps a Subsidiary of Seleucia on the Tigris"@en ;
    skos:inScheme nm: ;
    skos:prefLabel "Uncertain Mint 52"@en ;
    skos:related [ un:hasUncertainty nm:uncertain_value ;
            rdf:value nm:seleuceia_ad_tigrim ] ;
    skos:scopeNote "This concept should be used only in the context of Seleucid coinage."@en .

In addition to this, we now make it possible to link an attributable workshop to the broader concept of the mint within its field of numismatics. In Seleucid coinage, for example, there are two distinct workshops of Babylon, Babylon I and II. Both of these mints link to nm:babylon as a skos:broader. In these cases, as with the uncertain mints, the RDF for these concepts does not contain specific geographic coordinates, but it is possible to extract them via SPARQL or other API calls.

On the user interface side of things, Numishare has been updated to extract the coordinates from parent or related mints and include them in various geographic data serializations, like KML and GeoJSON. Uncertain mints are styled in gray to differentiate from the usual blue color.

See for example.

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