Tuesday, March 24, 2020

First batch of Philip II coins added to PELLA

The first few collections of Philip II coins have been linked to new Le Rider URIs and have been made accessible in PELLA through Nomisma.org's SPARQL endpoint. The American Numismatic Society linked 656 coins to these new URIs. Over the weekend, Karsten Dahmen at the Berlin Münzkabinett cataloged the first 17 coins of their collection. Additionally, I used Matt Lincoln's old data dump of years-old British Museum RDF data running locally in an endpoint to query for Le Rider references among their coins. Using OpenRefine to perform some additional cleanup, almost 60 coins of Philip II from the British Museum are now available in PELLA. Furthermore, just about a half hour ago, Julien Olivier at the Bibliothèque nationale de France sent a spreadsheet of 202 coins of Philip II with their corresponding Le Rider URIs. At this phase, there are now over 900 physical specimens linked into these typologies in PELLA. Not bad since we only just published them less than a week ago!

PELLA Philip II 137 is one of the best-represented types.

I expect a lot more contributors to come along as the cataloging process begins to proliferate through partners such as KENOM and NUMiD.

As it stands now, there are 382 total parent types in PELLA. The coins from the aforementioned collections are cataloged with a mixture of Le Rider (subtype [skos:broader] or skos:exactMatch [for plate-figure numbers]) URIs and PELLA parent type URIs. With the following SPARQL query, I can get a count of the number of photographed specimens per type:

PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX dcterms: <http://purl.org/dc/terms/>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX nm: <http://nomisma.org/id/>
PREFIX nmo: <http://nomisma.org/ontology#>
PREFIX skos: <http://www.w3.org/2004/02/skos/core#>

SELECT ?type (count(?coin) as ?count) WHERE {  
  ?type dcterms:source|skos:exactMatch/dcterms:source nm:pella_type_series .
  ?coin nmo:hasTypeSeriesItem|nmo:hasTypeSeriesItem/skos:broader ?type .
  {?coin nmo:hasObverse/foaf:depiction ?img}
  UNION {?coin foaf:depiction ?img}
} GROUP BY ?type

Hoards of Philip II coins
There are 258 types of Philip II with at least one photographed specimen, which is about two-thirds of the entire range of coinage. Not too bad for just several collections working together to catalog their coins in a few days.

Now that we have linked the Philip II Nomisma ID to typologies and specimens, some of these specimens also include hoard references, therefore populating the Philip II URI with additional research context for geographic and statistical visualization.

Average weights of tetradrachms from Philip to Alexander

As you can see from the chart above, the weight of Macedonian tetradrachms remains consistent from Philip II to Alexander until 336 B.C (https://bit.ly/2wCuH8G).

Thursday, March 19, 2020

The gold and silver coinage of Philip II published to PELLA

After considerable effort by ANS curator Peter van Alfen, the gold and silver coin types of Philip II of Macedon have been published to PELLA. This typology, based on Georges Le Rider's 1977 Le monnayage d’argent et d’or de Philippe II frappé en Macédoine de 359 à 294, has been numbered 1-382. Le Rider's corpus is actually a die study, and the numbering system is based on die combinations rather than types. As such, there are about 2,200 or so die combinations that correspond to the 382 types. These types were given a new numbering scheme, pella.philip_ii.1 to 382, but all of the Le Rider numbers are also URIs in order to establish a concordance between Le Rider and the new scheme so that collections that cataloged their coins with Le Rider numbers can submit their RDF with those URIs or map the Le Rider to the PELLA type number.

Le Rider numbers as subtypes or deprecated types

The correspondence between PELLA and Le Rider numbers is either 1:n or 1:1. When a typology has multiple possible die combinations, the Le Rider number is considered to be a subtype of the PELLA super type. For example, there are three die combinations for PELLA Philip II no. 1, Le Rider 1.1 to 1.3. If a museum has cataloged one of their coins to Le Rider 1.1, that coin will show up on the subtype page for that combination as well as the page for PELLA Philip II 1, which gathers all of the physical specimens linked directly to that URI or any possible subtype URI (via Nomisma.org's SPARQL endpoint).

Philip II 125 with the first specimen from a Nomisma partner.

The other category in which a PELLA and Le Rider number might correlate is 1:1. In these cases, the Le Rider URI still exists, but is not a subtype (linked in the RDF as skos:broader). Instead, the Le Rider Linked Open Data is dcterms:isReplacedBy the PELLA URI, which forces an automatic semantic HTTP 303 redirect in the browser (e.g., Le Rider 5.120). The underlying RDF for the Le Rider URI is still accessible through content negotiation or appending .ttl, .jsonld, or .rdf onto the URI. These two URIs are still linked together by skos:exactMatch, which facilitates the display of coins linked to Le Rider URIs on the PELLA page.

Uploading spreadsheets in Numishare

The publication of this typology represents a breakthrough in another way. Last summer, I spent several weeks developing a spreadsheet import mechanism in the Numishare back-end. I detailed it here (along with recommendations for structuring numismatic data in Google Sheets). After some further tweaking this week, the Philip II typology is the first spreadsheet data imported into Numishare in production. Out of all of the typology projects we have published online in the last 8 years (since the OCRE prototype developed in 2012), this is the first one that did not require me to write an intermediate PHP script. I cannot overemphasize how important this is. Curators can now formulate their own data, according to the specifications above, and publish new projects without technical intervention. After the conclusion of the Hellenistic Royal Coinages project in May, I will turn my attention to refactoring older spreadsheets from OCRE into this new format, and major updates in OCRE can be made directly by curators. I have essentially coded myself out of a repetitive task, saving myself a lot of time and the ANS a lot of money in the long term.

What's next for PELLA?

Now that the URIs for Philip II are activated, I imagine that our colleagues in Berlin and Paris will begin cataloging with them. Peter has updated our curatorial database with these new IDs, but the data have not been pushed from our [terrible] FileMaker database to Mantis, but you should expect to see the ANS's coins of Philip II online in the coming days. In the mean time, a single tetradrachm from the Fralin Museum at the University of Virginia is the first contributor to the new corpus, for Philip II 125.

Tuesday, March 10, 2020

About 800 "Greek" concepts published to Nomisma

After two weeks of solid research and data entry labor by Andy Meadows and I (and after review by the Greek committee), about 800 new or updated concepts corresponding to the Greek world have been published to Nomisma.org in three spreadsheets. These entities include people (rulers, usually) and their associated dynasties and corporate entities. Aside from people and organizations we typically consider "Greek", these lists include entities from other domains that have always been historically part of the study of broader Greek coinage, including Parthian, Indo-Scythian, Numidian, Arabian, etc. These entities aren't a comprehensive listing of every possible ruler that issued coinage from a particular realm, but form a large portion of these rulers, reflecting the combination of an older spreadsheet of rulers with the entities necessary for the publication of a new Inventory of Greek Coin Hoards database (as part of the NEH-funded Hellenistic Royal Coinages project). Corporate entities can be separated into their own spreadsheets for further revision by subject specialists in order to fill in gaps.

What's useful is that while we are able to use the W3C Org ontology to link people to their roles in larger corporate entities (and the start and end dates of their reign(s)), we are also able to apply the same org:Membership model to link one foaf:Organization to a larger one. That is to say, the Kingdom of Cimmerian Bosporus was independent from 438-107 B.C., but from 107 to 63 was part of the Kingdom of Pontus, and from 63 B.C. to 370, operated as a client-kingdom of Rome.

This enables us to execute queries for all of the lesser kingdoms that served as client-states of Rome:

  ?org a foaf:Organization ;
         org:hasMembership/org:organization nm:roman_empire ;
         skos:prefLabel ?label FILTER (langMatches(lang(?label), "en"))

This can be taken a step further to list the client-kings of Rome by means of the link between the ruler and their kingdom and dates of their reign and filtering it against the date range in which that kingdom was a client-kingdom of Rome.

SELECT ?person ?p_label ?p_start ?p_end ?org ?label WHERE {
?org a foaf:Organization ;
         org:hasMembership ?membership ;
         skos:prefLabel ?label FILTER (langMatches(lang(?label), "en")).
  ?membership org:organization nm:roman_empire ;
              nmo:hasStartDate ?client_start;
              nmo:hasEndDate ?client_end .
  ?person org:hasMembership ?pMembership ;
          skos:prefLabel ?p_label FILTER (langMatches(lang(?p_label), "en")).
  ?pMembership org:organization ?org ;
               nmo:hasStartDate ?p_start ;
               nmo:hasEndDate ?p_end .
  FILTER (?p_end > ?client_start && ?p_end < ?client_end)
} ORDER BY ?org ?p_start

The query above results in the following table of rulers sorted chronologically. The first client-king of Bosporus is Pharnaces II, the son of Mithradates VI, who took over in 63 B.C.

Now that the publication of these entities is complete, I will turn my attention back to reconciling authorities in IGCH data in OpenRefine. The new coin hoard database should be ready by the end of March, and it will facilitate new modes of query that include querying by dynasty and corporate entity by means of the person-org/dynasty relationship inherent in Nomisma's LOD data model. Greek numismatists will finally have a decent open access tool for coin hoard research, coupled with the publication and interlinking of our archival records in Archer.

Wednesday, January 8, 2020

A closer look at the Nomisma monogram data model

After the launch of more than 1,200 monograms that appear on the coinage of Alexander the Great as part of the PELLA project, I have made some updates to the data maintenance framework that underlies Nomisma.org. These changes enable monogram datasets to be added/removed via revised SPARQL/Update queries that incorporate CIDOC CRM properties to link to image files and the W3C PROV ontology for data provenance (similar to the model we already implement for Nomisma concept URIs). Note that the PROV ontology is not used for data provenance for coin type corpora or hoard databases, although this is something we should consider implementing at some point.

Introduction to the Monogram/Symbol data model

Monograms published to the web follow a similar pattern to other SKOS concepts in our ecosystem. The RDF class is nmo:Monogram from the Nomisma ontology. Our ontology will be updated soon to give nmo:Monogram a superclass of CIDOC CRM's E37_Mark. Any other symbol that appears on a coin (which can be letters used as control marks or mint marks and pictographic symbols, such as "torch" or "ram's head") are also E37_Marks. The definition of a Mark is as follows:

This class comprises symbols, signs, signatures or short texts applied to instances of E24 Physical Man-Made Thing by arbitrary techniques in order to indicate the creator, owner, dedications, purpose, etc.

All symbols are inherently concepts and have one required skos:prefLabel and one skos:definition in English. Like other concepts, there might be a Field of Numismatics (dcterms:isPartOf) or Bibliographic reference (dcterms:source) pointing to Nomisma URIs.

Since all symbols are E37_Marks (directly or indirectly), we are able to use some other CIDOC CRM properties. The crm:P106_is_composed_of property points to constituent letters or symbols. Typically, this is letter, but we have at least a few examples of RIC 10 monograms that are composed of letters and Christograms. When we publish a new edition of these monograms into OCRE, we are going to create the Christogram URIs in a new /symbol/ namespace in Nomisma.org. Using property paths, it will be possible to execute a SPARQL query for any monogram that includes a Greek rho, regardless of whether this letter appears directly in the monogram or is part of a monogram that is contained within a monogram.

  a nmo:Monogram, skos:Concept ;
    <http://numismatics.org/pella/symbol/monogram.price.1000#provenance> ;
  void:inDataset <ttp://numismatics.org/pella/> ;
  crm:P106_is_composed_of "Κ", "Υ", "Ο" ;
  skos:prefLabel "Price Monogram 1000"@en ;
  skos:definition "Monogram 1000 from M.J. Price, Coinage in the Name of Alexander the 
    Great and Philip Arrhidaeus: A British Museum Catalogue. The monogram contains 
    Κ, Υ, and Ο as identified by Peter van Alfen."@en ;
  dc:source <http://nomisma.org/id/price1991> ;
  dc:isPartOf <http://nomisma.org/id/greek_numismatics> ;
    <http://numismatics.org/symbolimages/pella/monogram.price.1000.svg> .

We link to one or more digital image files representing an idealized view of the monogram or symbol with the property, crm:P165i_is_incorporated_in. At the recommendation of the CRM SIG, this digital image (an SVG file: see Github for the full repository of monograms SVGs) bears a crmdig:D1_Digital_Object class and some additional triples about the license (CC Public Domain Mark), the ORCID of the graphic artist who drew them (Mark Pyzyk), and the mime-type as dcterms:format.

  a crmdig:D1_Digital_Object> ;
  dc:format "image/svg+xml" ;
  dc:creator <https://orcid.org/0000-0001-7542-4252> ;
  dc:license <https://creativecommons.org/choose/mark/> .

Like Nomisma concepts, these monograms have some provenance metadata, linking them to Peter van Alfen's Nomisma editor URI as the contributor (of the constituent letters) and a link to a source Google Spreadsheet. These monograms were imported into PELLA through a new symbol spreadsheet import functionality implemented in the Numishare platform itself. It operates much like the spreadsheet import in Nomisma, parsing the spreadsheet and transforming rows into RDF files that get stored in Numishare's eXist-db XML database.

While there is a basic interface built into PELLA (and other monogram corpora when they get published in Numishare) to query by constituent letter based on XQuery of the XML database, ultimately, I plan to implement a unified interface for this sort of query directly in Nomisma.org which will be based, instead, on SPARQL (see this basic example query). This will open the door to querying across many type corpora (Seleucid and Ptolemaic coinage combined), as well as exploit the relationships between letters, monogram URIs, and coin types that have been linked to those monogram URIs, paving the way to extract lists of mints, authorities, etc. connected to certain letters, and sort these by chronology or other categories. This is merely the tip of the iceberg in new forms of query of numismatic data that were never previously possible at this scale, made possible by Linked Open Data methodologies.

Friday, December 20, 2019

1200 Hellenistic monograms posted to PELLA, and OCRE updates

As part of the larger NEH-funded Hellenistic Royal Coinages project, we have published over 1200 monograms (and open access SVGs) to PELLA through a new spreadsheet import mechanism in Numishare that is very much like the one we use for IDs in Nomisma. I have also updated the monograms for RIC 10 that had been published to OCRE already.

The data model follows recent agreements for crm:P106_is_composed_of for constituent letters and crm:P165i_is_incorporated_in for 1 or more digital images, as also recommended by the CIDOC CRM sig. Non-monograms are E37_Mark.

We haven't connected PELLA monograms to Price Alexander coin types yet, but that will be coming pretty soon. You can, however, take a look at what's possible in OCRE (http://numismatics.org/ocre/symbol/monogram.ric.10.marcian.1), with a monogram displaying a map of related mints and a list of coin types.

The /symbols interface has a very simple system of selecting constituent letters, e.g., http://numismatics.org/pella/symbols?symbol=%CE%A0&symbol=%CE%A3

I plan to build something more sophisticated in Nomisma.org that utilizes SPARQL of monograms aggregated from disparate datasets which will also allow more complex queries based on mint, authority, etc. based on connections between monograms and coin types (including geographic visualization).
This is the first step of facilitating some major research questions in Greek numismatics.

Merry Christmas!

Thursday, November 7, 2019

New Partners for Nomisma

Several new partners have joined the Nomisma.org numismatic Linked Open Data ecosystem through the database network developed through the Berlin Münzkabinett. This software framework, which is used by about 20 collections in Germany and Austria, now supports the direct-to-Nomisma RDF export detailed in Nomisma.org's documentation. Previously, I had written a PHP script to harvest LIDO XML files (one by one) that were listed in text files from each institution. At one HTTP request per second, it typically took about three hours to generate an RDF export for Berlin that I stored as a static file on the numismatics.org server. Now, it takes only a minute or two to ingest RDF VoID dataset metadata and data dumps directly from the Berlin database.

Now, about three-quarters of the 40 or so collections that contribute data to Nomisma offer direct RDF exports according to our specifications, which is a tremendous advancement toward sustainability of our ingestion workflow. KENOM offers an OAI-PMH API that I have scripted to harvest, and harvesting from the Bibliothèque nationale de France is a combination CSV processing/Gallica OAI-PMH harvesting. The remaining partners have been added into Nomisma by writing bespoke scripts for processing CSV into RDF and storing static files on the ANS server (often, this process includes having to use OpenRefine to map coin type references to URIs). I am hoping that in the next few years, we can transition completely to direct RDF ingestion via our VoID specification or Linked Art JSON-LD harvesting, which I have already begun to prototype in the Nomisma.or backend.

New partners include:
  • Augsburg University
  • Konstanz University
  • Mainz University
  • University of Vienna

These add more than 1,000 coins into Nomisma.org, primarily for OCRE and CRRO.

Friday, September 27, 2019

First pass at processing Linked Art JSON-LD to Nomisma RDF

Over the last few weeks, I have been developing a harvester for Linked Art-complaint JSON-LD simultaneously in both Nomisma.org and Kerameikos.org, which share similar frameworks that are built around Orbeon XForms for manually editing or transforming large quantities of data (usually CSV) to RDF, and connecting these workflows directly to Apache Solr and a SPARQL endpoint. These new features, in both platforms, load JSON-LD from a URL, which is transformed into the XForms 2.0 spec's JSON-to-XML model, and is then validated and parsed into RDF/XML on the way into the SPARQL endpoint.

I will write something more comprehensive about how this functions specifically on the Greek pottery side of things, but I have successfully tested transforming the Linked Art JSON-LD for a test coin (http://numismatics.org/collection/1944.100.76933.jsonld?profile=linkedart) into the Nomisma.org hybrid data model that is composed of properties and classes from our own numismatic ontology and properties from other ontologies, like Dublin Core Terms and the Europeana Data Model.

This transformation process removes much of the developer-oriented cruft out of the JSON to distill the model specifically to the essential literals and URIs necessary for connecting a coin, its measurements, images, and coin type URIs to the numismatic knowledge graph in the Nomisma.org SPARQL endpoint.

Basically, it performs the following functions:

  • Maps the preferred term for an object dcterms:title and the accession number to dcterms:identifier
  • Measurements (weight, axis, diameter) are mapped to the correct Nomisma property and validated to ensure that they conform to the correct units. Inches and centimeters will be converted to millimeters for diameter, height, width, and thickness.
  • Images for each "part" (obverse, reverse) are placed into the appropriate nmo:hasObverse or nmo:hasReverse data object as foaf:depiction. IIIF service URIs are expanded into the edm:WebResource and svcs:Service model that we have appropriated from the Europeana Data Model specification.
  • Any top-level "type" (classified_as) that is not a Getty or Nomisma URI is presumed to be a coin type. We would like to discuss this further with the Linked Art community to formalize a method by which we can flag coin type URIs in a more stable and consistent manner.

It should be noted that Linked Art hasn't delved deeply into provenance, which would be necessary for encoding coin hoard URIs and findspot metadata.

You can see the resulting RDF/XML (that would get sent into the Nomisma SPARQL endpoint) here: https://gist.github.com/ewg118/049046755a670c3645689c68c14e794b.

This harvester will be adapted as changes are made to the Linked Art model. We hope that this feature in Nomisma will open the door to more streamlined and consistent aggregation of numismatic materials from the broader museum community, especially as we begin to work on new projects that are relevant to the American Art Collaborative.