=Paper=
{{Paper
|id=Vol-3724/paper3
|storemode=property
|title=Publishing Numismatic Public Finds on the Semantic Web for Digital Humanities Research – CoinSampo Linked Open Data Service and Semantic Portal
|pdfUrl=https://ceur-ws.org/Vol-3724/paper3.pdf
|volume=Vol-3724
|authors=Heikki Rantala,Eljas Oksanen,Frida Ehrnsten,Eero Hyvönen
}}
==Publishing Numismatic Public Finds on the Semantic Web for Digital Humanities Research – CoinSampo Linked Open Data Service and Semantic Portal==
https://ceur-ws.org/Vol-3724/paper3.pdf
Publishing Numismatic Public Finds on the Semantic
Web for Digital Humanities Research – CoinSampo
Linked Open Data Service and Semantic Portal
Heikki Rantala1 , Eljas Oksanen2 , Frida Ehrnsten2,3 and Eero Hyvönen1,2
1
Semantic Computing Research Group (SeCo), Aalto University, Finland
2
University of Helsinki, Finland
3
National Museum of Finland
Abstract
This paper presents the new web demonstrator and Linked Open Data (LOD) service CoinSampo. The
data service is based on over 18 000 numismatic citizen science finds that were reported to the National
Museum of Finland between 2013 and 2023, and which are enriched using external data sources by
data linking. The data has been converted to LOD using light-weight facet ontologies. The CoinSampo
web application offers users faceted semantic search and various integrated data-analytic visualization
options. The application is aimed at a broad range of user audiences, including scientific researchers,
heritage professionals, citizen scientists, amateur archaeologists, educators, and anyone interested in
learning about the past.
Keywords
Linked Open Data, Numismatics, Archaeology, Digital Humanities,
1. Introduction
The number of metal-detected archaeological objects that have been recovered and reported by
members of the public in Finland has considerably increased over the last ten years. Whereas
the Finnish Heritage Agency (FHA) redeemed between 2000 and 2009 a total of 439 public finds
into the national collections, today that number is nearing 2000 per annum [1, 2, 3]. Among
these objects, coin finds have several characteristics that set them apart. Coin finds are usually
one of the most, if not the most, common objects reported by the public (e.g., in the UK [4, 5]).
Coins can be identified more precisely than many other common finds, producing higher quality
record data and making them specially suitable for being described semantically as well as for
Digital Humanities (DH) analysis. For example, authorities (rulers or institutions in whose name
coins were issued) and mints (places where coins were struck) lend themselves naturally to being
described by controlled vocabularies and ontologies. Historical coins moved internationally,
making harmonizing and comparing international data especially relevant.
$ heikki.rantala@aalto.fi (H. Rantala); eljas.oksanen@helsinki.fi (E. Oksanen); frida.ehrnsten@helsinki.fi
(F. Ehrnsten); eero.hyvonen@aalto.fi (E. Hyvönen)
0000-0002-4716-6564 (H. Rantala); 0000-0002-7468-9256 (E. Oksanen); 0000-0002-7257-4818 (F. Ehrnsten);
0000-0003-1695-5840 (E. Hyvönen)
© 2024 Copyright for this paper by its authors. Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0).
CEUR
Workshop
Proceedings
http://ceur-ws.org
ISSN 1613-0073
CEUR Workshop Proceedings (CEUR-WS.org)
CEUR
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Workshop ISSN 1613-0073
Proceedings
The rapid increase in metal-detected finds in Finland parallels what is happening in several
other European countries where metal-detecting is legal (albeit always with restrictions). While
this new material has considerable advanced archaeological knowledge of the past, as well as
arguably democratized and increased appreciation towards cultural heritage in general, it has
also burdened traditional heritage management workflows and created significant new demands
to open the data to researchers and the public – including the detectorists and citizen scientists
who have recovered the finds in the first place [6, 7, 8].
As a solution to these challenges, this paper presents the demonstrator web application
and LOD service CoinSampo, a new member in the Sampo series of systems [9]. CoinSampo
was created using open data about numismatic public finds reported in Finland between 2013
and 2023. The CoinSampo web application1 and data service2 were opened to public on 28th
February 2024. The knowledge graph (KG) includes some 620 000 triples and contains data
about over 18 000 individual numismatic objects in RDF3 format. The KG can be queried using
SPARQL4 query language from an open read-only endpoint5 . The data is served through the
Linked Data Finland6 service, which, for example, takes care of resolving URIs.
CoinSampo was created as part of the DigiNUMA – Digital Solutions for European Numismatic
Heritage7 [1, 10, 11] project in response to new needs in Finnish and international Cultural
Heritage (CH) data management, research, and dissemination using LOD. The data service
and web application builds upon the FindSampo8 [12] system, which has opened data of some
3000 archaeological public finds of all types that have been catalogued, acquired and redeemed
into the national collections of the FHA. Since only prehistoric and medieval (before AD c.
1560) finds are consistently redeemed and recorded by the FHA, however, if this was the only
source of public finds data a huge amount of later archaeological finds material would never be
available. Unlike FindSampo, therefore, CoinSampo opens key data extracted from coin finds
reports sent in by the public to the FHA, even if the numismatic objects themselves are never
seen by heritage professionals or catalogued in a collections management system.
CoinSampo and its data, therefore, promote not only a paradigm shift in how cultural
heritage knowledge can be effectively disseminated, but also in what kind of cultural heritage
data institutions should aim to create today. This includes not only records of individual objects
made “worthy” of being physically archived because of their age or rarity, but of all manner of
archaeological finds, even of common objects, because as aggregate mass data they may reveal
completely new patterns that are of great relevance to understanding our shared past.
This paper is partially extended from a demo paper [13], and is structured as follows: First
we present a summary of the current state-of-the-art in terms of European public finds data
services and portals, and numismatic DH infrastructure. This is followed by a discussion of
the CoinSampo data, data model, and a description of the web application. We demonstrate
1
https://coinsampo.ldf.fi
2
https://www.ldf.fi/dataset/coinsampo
3
https://www.w3.org/RDF/
4
https://www.w3.org/TR/rdf-sparql-query/
5
The endpoint can be queried at https://ldf.fi/coinsampo/sparql. The endpoint is set up using Apache Jena
Fuseki: https://jena.apache.org/documentation/fuseki2/.
6
https://www.ldf.fi/
7
Project homepage: https://seco.cs.aalto.fi/projects/diginuma
8
https://loytosampo.fi/en
CoinSampo’s potential as a platform for conducting scientific research and for effectively
disseminating complex archaeological and numismatic material. Finally, we conclude with a
critical reflection on lessons learned during research.
2. Related work
A considerable amount of work has been conducted in the recent years on developing platforms
and data services for European cultural heritage data, with recent transnational efforts including
the European Cultural Heritage Cloud9 and the ARIADNEplus10 [14] portal. ARIADNEplus
is a pan-European research infrastructure and aggregation project for all archaeological data,
but coin finds data (as a major category of archaeological finds) naturally forms a substantial
part. Targeting numismatic knowledge, Nomisma.org11 [15] is a collaborative international
project that aims to provide the necessary LOD ontologies for representing numismatic concepts.
Nomisma data has been used to create multiple web applications, such as the Seleucid Coins
Online12 . However, Nomisma is currently mainly focused on the classical era, which limits it’s
applicability to Finnish data.
Online portal have been established in several European countries for opening specifically
archaeological public finds data, notably in Belgium (MEDEA13 ), the Czech Republic14 , Denmark
(Digitale Metaldetektorfund, DIME15 ), England and Wales (PAS16 ), Estonia17 , and the Nether-
lands (PAN18 ). Each has, invariably, approached the dissemination of the finds data from local
perspectives, and according to the prevailing national cultural heritage management priorities.
These in turn have shaped the technological solutions adopted. In the Netherlands, for instance,
considerable attention has been paid to developing object typologies, with illustrated reference
guides to artefact types built into the portal interface [16]. This is being develop as an important
scientific and citizen science resource on its own right, which may assist heritage professionals
by “crowd-sourcing” object identification and recording. In Estonia the finds portal permanently
obfuscates the locations below a sub-regional level of c. 100 km2. Whereas in some other
countries (including Finland) the precise findspot location of an object is published once it has
been processed by heritage professionals, in Estonia this is not done because of heightened
concerns over looting of vulnerable archaeological sites [6].
A certain amount of tailoring to local circumstances is therefore the norm. On a broader
conceptual level, however, the above finds portals offer little by way of powerful tools, beyond
simple map applications, to visualize important patterns and archaeological phenomena in the
data. This is typical of cultural heritage data services at large. These tend to be build upon a
paradigm derived from the traditional knowledge representation scheme of the field: printed
9
https://data.europa.eu/doi/10.2777/64014
10
https://ariadne-infrastructure.eu
11
http://Nomisma.org
12
https://numismatics.org/sco/
13
https://vondsten.be
14
https://amcr-info.aiscr.cz/?page=pas
15
https://www.metaldetektorfund.dk
16
https://finds.org.uk
17
https://leiuatlas.ee
18
https://portable-antiquities.nl
museum catalogues. Objects are opened to the user as individual entries, often richly described
but not very effectively located in a larger context that could be provided either by the contents
of their collection as a whole or by wider LOD resources (cf.[1]).
The potential for “big data” analysis of public finds, however, has been explored and exploited
in archaeological research already for some time [17, 18, 19]. CoinSampo deploys a series of
data visualization tools developed to fit the archaeological particularities of the dataset, as
well as links to external resources relevant for understanding the rich historical phenomena
represented by the numismatic material. It presents a model for democratizing not only access
to digitized cultural heritage, but also to data analysis more generally.
3. Data
The CoinSampo KG was created using data collected at the Finnish National Museum based on
reports sent by members of the public who have found old coins, usually through metal detecting.
The data was collected between 2013 and 2023 as a tabular Excel file with the aim of recording
all coin finds reported during that time period in Finland. With some exceptions, this material
consists of coins that are more than 100 years old and thus protected by the current Antiquties
Act19 . The original tabular data includes the following fields for each object: find municipality;
more exact location of the find site such as the village; northern find coordinate (y); eastern
find coordinate (x); context of the find such as field or forest; authority; denomination; mint;
country; period; material; numismatic type; earliest possible date of minting; latest possible
date of minting; finder name; date of finding; free-text field for additional notes; ascension (i.e.
FHA national collection) number; weight. Because of privacy reasons and the European Union’s
GDPR legislation20 finder information is not included in the public CoinSampo KG. The exact
find coordinates of redeemed finds (generally medieval or older) that have not yet been fully
processed by the FHA have also been omitted for reasons of protecting particularly vulnerable
archaeological sites. Moreover, as soil finds some of the objects are in such a bad shape that
exact definitions are impossible to determine even by an expert.
Initially the Excel file was used only to keep track of the finds. Before about 2015 finds were
reported in various ways and without any standardized reporting platform. As the number
of finds increased, it soon became evident that their handling had to be rationalized. All find
reports were directed to a common e-mail address. In addition, return forms were introduced
for finds not taken into the collections. In 2019 the Finnish Heritage Agency launched the
Ilppari reporting service for all archaeological finds made by citizens. The online service has
significantly increased the number of finds reported to the authorities, also providing more
detailed coordinate information on the find location. Over the last five years, the recording of
coin finds has developed accordingly, enabling systematic data processing.
During the development stage for CoinSampo, the Excel file was improved and expanded
several times. Information was added, for example, on materials and dating, as well as hier-
archical information on the coins’ region of origin and mint. Furthermore, ontological work
and data cleaning was conducted with the aim of removing typos and parallel concepts. The
19
https://www.finlex.fi/fi/laki/ajantasa/1963/19630295#L2
20
https://eur-lex.europa.eu/eli/reg/2016/679/oj
conversion process of the data to RDF format was made by a repeatable Python script. In the
conversion process the data was first converted using literal values, and object values were
added in a second phase. This means that the original literal forms of the terms used in the
Excel file are retained in the CoinSampo KG.
The CoinSampo Data Model (CSDM) was created to represent this data. The cen-
tral properties of CSDM are given in Table 1. The namespace used for CSDM schema
is . The examples in this paper use prefix
cs for this namespace. The table also lists the number of coin finds with that
property and gives the equivalent properties in the Nomisma.org ontology (namespace
prefix nmo:). As a data model [20] CSDM is mainly
focused on the specific needs of the Finnish coin data, as opposed to an universal ontology such
as that produced by Nomisma.org, which is meant for more generic use. CoinSampo also uses
some properties derived from Simple Knowledge Organization System SKOS21 , FindSampo, and
Basic Geo22 . For example, the labels and broader concept relations are expressed with SKOS
and the coordinates using Basic Geo.
Property C num. Nomisma Explanation
cs:denomination 1 18342 nmo:hasDenomination Face value of a coin.
coins:context 1 18342 nmo:hasContext Find context of a coin.
coins:period 0..1 18323 nmo:hasProductionDate Production period of a
coin find.
cs:material 0..1 18304 nmo:hasMaterial Main material of a coin.
cs:municipality 0..1 18302 nmo:hasFindSpot Municipality where a
coin was found.
cs:country 0..1 18232 nmo:hasMint Country or region where
a coin was minted.
cs:authority 0..n 13394 nmo:hasAuthority Authority (ruler) in
whose name a coin has
been issued.
cs:mint 0..1 13311 nmo:hasMint The place where a coin
has been minted.
cs:numismatic_type 0..n 2151 nmo:hasObjectType; Refers to possible mis-
nmo:hasPeculiarity; cellaneous numismatic
nmo:hasScholarlyName type of a coin.
Table 1
Main object properties in CoinSampo data model, with their corresponding Nomisma.org properties.
To represent the concepts in the data, multiple light weight ontologies or vocabularies were
created from the data for concept types such as authorities, mints and denominations. These
vocabularies are in this paper referred mainly as “facet ontologies”. These facet ontologies
include hierarchies and are linked to external resources, mainly Wikidata [21], where possible.
Wikidata has been used to enrich the ontologies in various ways. While the facet ontologies are
21
https://www.w3.org/2004/02/skos/
22
https://www.w3.org/2003/01/geo/
created mainly for the purposes of exploring and visualizing the CoinSampo KG (eg., by using
hierarchical facets or showing coordinates of mints on maps), they could also be used as a basis
for vocabularies of similar data sets, such as coin finds from neighbouring countries.
Facet ontologies were created for find municipalities, authorities, mints, countries, denomina-
tions, contexts, materials, and numismatic types. This was done by outputting all the terms
used in each of these fields as CSV files, and then going through them systematically to remove
duplicates and correct errors, so that only the desired ontology of concepts and their preferred
labels remained with each line corresponding to a single concept. The URI of each concept was
created using the Finnish label as the local identifier. Duplicate terms and common incorrect
forms were retained as hidden labels in their own column for each concept.
The facet ontologies were mapped to Wikidata and/or the Finnish ontologies 23 MAO/TAO
(Ontology for Museum Domain and Applied Arts) or YSO (General Finnish Ontology). These
mappings were mostly done manually in CSV files. Wikidata was queried with SPARQL to
enrich the facet ontologies in a number of ways, including extracting coordinates, images, and
descriptions. Mappings to the Nomisma.org ontology and the Numista.com service were also
extracted from Wikidata for mints and authorities. All the instances in facet ontologies include
English labels in addition to Finnish ones. Many of these were added automatically through
Wikidata or YSO mappings, though in some cases a translation had to be added manually.
Hierarchies were also defined in the CSV files for concepts using a separate column24 . Finally,
the facet ontologies were converted to RDF based on the CSV files using a Python script. The
classes of facet ontologies, number of instances, and explanations are given in Table 2.
Class Num. Explanation
coins:Municipality 242 Municipality, e.g., a town.
coins:Authority 193 Authority such as a ruler.
coins:Denomination 168 Face value of a coin.
coins:Mint 160 A place where coins have been minted.
coins:Context 49 General context of the find, such as “field”.
coins:Country 41 A country.
coins:Numismatic_type 34 Term describing the general properties of
numismatic object.
coins:Period 9 Historical time period.
coins:Material 6 Material of manufacture.
Table 2
Main classes in CoinSampo data model and the number of their instances in the facet ontologies.
A major difference between Nomisma and CSDM is that in Nomisma properties – such as
material, denomination and authority – are generally not expressed for individual coin objects.
Instead the objects refer to a “type series item” resource that contains information on the
material, denomination, and other properties related to that specific type of coin. Whether or
not to follow this was the major modeling question when CSDM was being developed. It was
23
For Finnish ontology service see https://finto.fi/en/.
24
For municipalities a slightly modified hierarchy from the Finnish place ontology YSO places (https://finto.fi/
yso-paikat/en/) was used.
decided that it would be too much work to develop the necessary ontological infrastructure
demanded by the “type series item” approach to cover all coin finds. This typological information
already existed in the CSV files in a format that expressed the data separately for each coin.
Adding the type series item resources would add more work. While the memory requirement is
larger when material, denomination, etc., is expressed separately for each coin, SPARQL queries
perform faster when querying information for coins using our approach because the property
paths are shorter.
When comparing the CSDM to Nomisma, it should be noted that Nomisma tends to include
properties for much more detailed description of coins. Nomisma also includes properties
such as nmo:hasIconography and nmo:hasCorrosion that can be used for much more detailed
structured description of coins, which the CoinSampo data lacks. Notably, in CSDM the property
cs:numismatic_type combines multiple different properties from Nomisma, since it is used for a
somewhat miscellanious set of characteristics that were not deemed worth the effort to make a
detailed semantic distinctions for. On the other hand, CSDM includes separate properties for
mint and country or region of origin. This is because while the exact mint cannot always be
determined due to the fragmented nature or the poor state of preservation of a given coin, it is
usually possible to identify the general geographical area in which the coin was minted. From
a research perspective it was desirable make a clear semantic distinction between these two
related properties.
Nomisma.org ontology does not currently cover well the concepts required to describe
Finnish coin finds. Out of the 160 mints in the CoinSampo data 44 currently have a mapping
to Nomisma.org, and out of the over 18 000 individual coins only 210 are connected to a mint
with a Nomisma mapping. For authorities, a Nomisma mapping exist currently for 34 out of
the 193 resources, and only 146 individual coins have an authority that is mapped to Nomisma.
The existing Nomisma resources for describing the authority or mint exist therefore only for
around one percent of all the reported coin finds in Finland. This is largely because Nomisma’s
ontological infrastructure of medieval and later coins has not yet been developed.
Finally, CSDM allows for uncertain or unclear concepts. These are defined as instances of
cs:Uncertain_concept in addition to their other classes. CoinSampo facet ontologies currently
include 17 such concepts. For example a number of historical coins found in Finland have clearly
been issued in either Denmark or Sweden but the mint cannot be determined more precisely. In
such cases a separate resource has been created, to represent the uncertain concept of, in this
example, “Denmark/Sweden”. These resources are mapped to the Wikidata resource of all the
possible individuals that the uncertain concept represents.
4. Web application
The CoinSampo web application 25 is based on the Sampo-UI26 framework [22, 23]. The applica-
tion works by creating SPARQL queries based on selections made by users and visualizing the
data using various JavaScript libraries. As an application based on Sampo-UI, CoinSampo consist
25
The source code of the portal is available at https://github.com/SemanticComputing/coinsampo-web-app and
the portal can be tested at https://rahasampo.ldf.fi/en/.
26
https://github.com/SemanticComputing/sampo-ui
of a front end mainly created using React27 and a back end using Node.js28 . The application can
be deployed easily using a Docker container.
The application is built to apply the concept of faceted search [24]. The data can be explored
and filtered using various facets representing entity properties. Coin finds can be filtered using
facets based on authority, mint, period or other properties. Each facet shows the hit count
for each individual selection. Facets are dynamic and the hit counts constantly update after a
selection is made in one of the facets. Because of this user can avoid searches that would not
return any results, and the hit counts offer further insight into data and help to explore it. The
default language of the application is Finnish, but the application can also be used in English.
The facet ontologies have English labels in addition to the Finnish ones, and the user interface
can dynamically switch between the language of the concepts by changing the language tag in
SPARQL queries (though the free-text “Notes” field is currently available only in the Finnish
language). In addition to the perspective for coin finds the CoinSampo web application also
offers search perspectives for searching and visualizing authorities and mints.
A basic use example of the application29 is shown in Fig. 1. A user has made two selection
using facets to filter the results. The period “18th century” has been selected from the Period
facet, and the broader region of “South Karelia” has been selected from the find discovery
Municipality facet. Because the municipality facet is hierarchical, the system selects all the
sub-concepts (municipalities) belonging to “South Karelia”. The result set consists of num150
individual coins, as can be seen in the top left corner. The default table view shows the most
important information about each individual coin as a record row, with a separate column
for each property. Each coin has their own instance page, which can be accessed using the
hyperlink on the table. Similarly important instances in the CoinSampo facet ontology – such
the authority “Peter the Great” or the period “18th century” – have their own instance pages.
The coins images shown in the table view are not of the individual coins themselves, as in
most cases this data is not available. Instead, CoinSampo shows images of similar kinds of
objects from the Finna30 service. Image links have been retrieved using Finna’s API31 through
creating search queries from coin properties such as authority, denomination, and material.
Clicking on an image opens the relevant search results page in Finna in a new tab.
The results can also be viewed in various ways by selecting one of the visualization tabs.
The visualization options include various types of charts and maps32 . The Use case section,
below, includes multiple examples of how these visualizations can be applied in analysis and
knowledge discovery.
27
https://react.dev/
28
https://nodejs.org/en
29
The examples are made using the desktop mode. CoinSampo can be used with mobile devices, and the interface
makes some adaptations for small screen, but the application works best on using a computer with a larger screen.
30
Finna service includes images uploaded by multiple Finnish museums. See: https://finna.fi/?lng=en-gb.
31
https://www.kiwi.fi/display/Finna/Finnan+avoin+rajapinta
32
The map in the example used in this paper is rendered using the Mapbox (https://www.mapbox.com/about/
maps/) service which is based on the OpenStreetMap (http://www.openstreetmap.org/copyright. CoinSampo also
uses maps provided from multiple other providers, such the National Land Survey of Finland.
Figure 1: Image shows the basic logic of the CoinSampo user interface. A user has made selections
using check box facets on the left and the result are shown on the right.
5. Use case
Coins from the Viking Age (here defined as 800–1150 AD) are well suited for demonstrating
the various functions of the CoinSampo data service. In Finland, as in the rest of northern and
eastern Europe, coins were at this time used as bullion and valued by their weight in silver.
This means that the denomination or origin of a coin was of limited importance, although
some coin types were certainly valued to a higher degree because of, e.g., their high silver
purity. The circulation of coins was therefore particularly international, creating interesting
contact patterns that linked vast areas in Europe and Asia. This was particularly so in Finland,
where coins arrived from western Asia and the Mediterranean via the great river routes of
modern Ukraine, Belarus and Russia, and over the Baltic Sea from Scandinavia, central and
western Europe [25]. See, for example, Fig. 2 created using the “migration” visualization tab: the
arcs connect the municipality of Hämeenlinna to the minting places of Viking Age coin finds
reported there, arriving from as far away as modern England, Germany, Iraq and Uzbekistan.
Finds reported by citizens have considerably changed the research situation regarding the
Viking Age coin circulation in Finland, creating a whole new body of material for understanding
the region’s pre-monetised economy. When Tuukka Talvio published his thesis on Viking Age
coin finds in Finland in 2002, the material available consisted of slightly over 7000 coins. Most
of these coins derived from hoards. Around 450 were recovered from excavated graves, and
Figure 2: A migrations visualization of Viking Age coins recovered near the town of Hämeenlinna
showing arcs between the find municipality and the places where the coins were minted.
only eighty from other excavations or as single finds[25]. The number of Viking Age single
find coins opened by CoinSampo is 836, or more than ten times this number.
A numismatic single find is generally described as a coin without connection to other finds,
whereas a cumulative find contains two or more singly found coins from a limited area [26].
Without further archaeological field work it is difficult to distinguish and categorize such finds
with certainty. As Talvio has noted, casual single finds tends to be whole coins, while cumulative
finds – possibly associated with dwelling sites – are more likely to consist of fragmentary coins.
One third (280) of the Viking Age coins in CoinSampo are fragments. The earlier the coin,
the more likely it is to have been cut into hacksilver and used as bullion. The high number of
fragments likely reflects silver use in connection to settlements and other activity sites, some
which may have been previously unknown. Previously, when coin finds mostly consisted of
hoards and grave finds, this was not well understood. Considerable scientific research potential
remains for work critically distinguishing and categorizing these different types of finds.
Because of the fragmentary nature of Viking Age coins in the Finnish finds material, it is not
always possible to produce a complete definition with exact determinations for all attributes.
For example, sometimes it is only possible to work out a general area of origin (e.g., “Germany”)
and not the exact minting place (e.g., “Köln”). Likewise in some cases it is impossible to date
the coin more precisely than within a century. And as seen in Fig.3, authority is undetermined
in more than half of of the entries.
It is nevertheless possible to extract a great deal of new information on the Viking Age coin
economy in Finland from the CoinSampo data. Using the faceted search it is easy to screen
different coin types. 327 (39 percent) of the recorded Viking Age coins are Islamic dirhams. The
majority of dirhams found in Finland are either of Abbasid (mostly ninth century) or Samanid
(mostly tenth century) origin. In his thesis Talvio estimated the number of Abbasid dirhams to
be around 900, and of Samanid dirhams less than 300. Most of the Abbasid coin was derived
Figure 3: The automatically created chart shows the defined minting authorities of Viking Age coins
added to CoinSampo. More than half are still marked as unknown.
from hoards in the Åland Islands, while Samanid dirhams were more commonly found in graves
on the mainland.
Figure 4: An aoristic chart showing the chronological distribution of dirhams in CoinSampo. The
periods of high level of import are clearly visible.
As Åland is a self-governing region with its own Heritage Administration unit, only sporadic
finds from there are included in CoinSampo. On the mainland, however, the number of dirham
finds has increased significantly and provides a completely new view on coin imports. So far
103 Abbasid and 133 Samanid dirham finds have been reported. As seen in Fig.4, coins from the
beginning of the tenth century are the most common. Significant quantities of this material
was not previously encountered on the mainland. Most coins are (as noted above) fragments
used as silver bullion and can probably be linked with Viking Age settlement sites.
The chronological and geographical distribution of the reported 485 western pennings does
Figure 5: Bar chart showing the distribution of western pennings according to province.
not differ greatly from that of the older hoards. Most date to the last decades of the tenth century
or the first half of the eleventh century. There are, however, an increasing number of coins
from the second half of the eleventh century. These were previously known mostly from hoards
discovered in eastern Finland, but not in the western part of the country [27]. The vast majority
of the new western coin finds are from the south-western coastal region of Finland Proper (see
Fig.5), which was undoubtedly the centre of Viking Age coin circulation as well as the area
were most of this silver entered the country. By narrowing search parameters, it is possible to
observe that finds from Finland Proper contain a higher proportion of certain generic German
coin types as Otto Adelheid -pfennings and denars minted in Köln. By contrast the distribution
of Anglo-Saxon (English) pennies and of the less common German coins is more evenly divided,
which may suggest different import routes. Cumulatively this new evidence begins to shed light
into such important but otherwise difficult to examine fields of research as Finnish prehistoric
inter-regional and international travel connections.
6. Conclusions and future work
LOD can be used not only to publish collection data for humans to read (first generation systems)
but also as data for analyzing collections using data-centric methods in DH (second generation
systems) [28]. CoinSampo tests and demonstrates this possibility in a novel application domain:
archaeological numismatics. Ontologies based on the concepts in the data and mapped to
external resources are used to enrich the data, and to make it easier to search, visualize, and
analyze it. We demonstrate how novel insights into collections data can be easily generated
by anyone without further specialist training in statistical software. CoinSampo democratizes
information about the past by making the data easy to access and examine, whether as individual
records or as an interconnected whole.
The demonstrator is an example of how practical and usable applications can be built easily
on top of SPARQL endpoints using the declarative Sampo-UI framework [23]. In addition
to the demonstrator presented here, we are also developing a more generic version of the
CoinSampo web application, which could be used to search and visualize any data that follows
the Nomisma.org ontology. For example, [11] presents an early version of CoinSampo with
international data.
A new data model was deemed the most convenient way to represent data in CoinSampo,
though the properties and classes can usually be mapped to the Nomisma.org ontology without
difficulty. Such mappings are useful when comparing local and international data. In many cases,
however, Nomisma is missing the concepts required to describe Finnish coin finds. While certain
simple cases, such as the material of manufacture, are straightforward to link to Nomisma, the
required concepts for representing mints and authorities exist only for around one percent of
the finds. Finnish coin finds (with only rare exceptions) are in European terms either medieval
or later, and these post-classical periods are still being developed in the Nomisma.org ontology.
Very importantly, there is also a difference between numismatic data obtained from old
museum collections – which often arrive from private collections or hoard finds, and where
the coins are in comparatively excellent condition – and data obtained from individual finds
recovered from the soil, usually from industrially ploughed fields. This difference is seen in the
quality of the available data. The latter are more likely to be fragmented and corroded, and any
data models and ontologies developed around them must take into account the fact that exact
determination of object properties may be difficult or impossible.
The broader research topic that this links to is the difficulty in modelling complex and often
uncertain cultural heritage information. Most archaeology deals with spatially and temporally
uncertain or “fuzzy” data, or with data where precise values cannot always be assigned to key
properties (here authorities, minting places, etc.). Knowledge organisation systems (such as
ontologies) arguably arise from pragmatic needs to model real world phenomena [29], and
therefore are a response to the particular needs, circumstances and material around which they
are constructed. In this context the development of a universal system, one that would reach
beyond its original source material, can be a particularly challenging aspiration.
This is highlighted in the CoinSampo research case, which brings in a new kind of source
material to digital numismatics (metal-detected soil finds), one which is typically damaged
or fragmentary. A knowledge organization system based on a different preconception of the
character of the base data – such as the Nomisma.org ontology, despite aspiring to be a universal
system within its domain – may therefore find it difficult to incorporate. CoinSampo offers
some examples of how to represent such data semantically, but the issue remains a challenge.
There is, therefore, a great deal of interdisciplinary and collaborative research left to be do in
order build semantic infrastructures that allow for a greater reuse and interoperability potential
in archaeological and numismatic, and more broadly in cultural heritage, data management at
an international level. This also includes effectuating a paradigm shift in how the act opening
cultural heritage data is conceptualised, towards a more integrated view that sees the contents
of collections not as a limited selection of discrete objects but as a connected body of material
that, when considered together, can tell more about the past than when apart.
Acknowledgements The project has been funded by the Jenny and Antti Wihuri Foundation
and the European Union’s Horizon 2020 research and innovation programme under the Marie
Sklodowska-Curie grant agreement No 896044. CSC – IT Center for Science has provided
computational resources.
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