Development of an ontology for modelling medieval manuscripts: the case of Progetto IRNERIO
10.6092/issn.2532-8816/11187
Il catalogo digitale di manoscritti medievali gestito dal Progetto IRNERIO è ricco di materiale di interesse legale, culturale e storico difficilmente accessibile e separato rispetto a contenuti esterni ad esso rilevanti. Questo articolo introduce un'ontologia chiamata Medieval Manuscripts Ontology (MeMO) e sviluppata per modellare questi manoscritti in modo da permettere agli studiosi di rappresentare, identificare, analizzare ed estrarre le informazioni in essi contenute. MeMO è stata sviluppata seguendo una metodologia robusta e agile, in modo da rispettare i requisiti richiesti dall'esperto di dominio (la preservazione della narrazione storica, la rappresentazione del contesto e la descrizione della collezione dei testi). MeMO, inoltre, è flessibile e riccamente documentata in modo da essere facilmente riusabile e estendibile in possibili scenari futuri. Quindi MeMO permette di modellare le risorse del Progetto IRNERIO con termini precisi per evitare una perdita di informazioni e supportare una miglior rappresentazione delle complessità concettuali che caratterizzano la collezione.
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Umanistica Digitale
Progetto IRNERIO
Development of an ontology for modelling medieval manuscripts: the case of Progetto IRNERIO
Text.Serial.Journal
https://umanisticadigitale.unibo.it/
Articles
2020-12-31
2020-06-19
2020-12-31
2021-04-01
117-140
Um. Dig.
Silvio Peroni
2020/12/31
10.6092/issn.2532-8816/11187
117
University of Bologna
2532-8816
9
Progetto IRNERIO
en
140
Zhitomirsky-Geffet, Maayan, and Gila Prebor. 2016. “Toward an Ontopedia for Historical Hebrew Manuscripts”. Frontiers in Digital Humanities 3. https://doi.org/10.3389/fdigh.2016.00003.
Development of an ontology for modelling medieval manuscripts: the case of Progetto IRNERIO
https://umanisticadigitale.unibo.it/article/view/11187/11879
    Umanistica Digitale - ISSN:2532-8816 - n.9, 2020
S. Barzaghi. M. Palmirani, S. Peroni – Development of an ontology for modelling medieval
manuscripts: the case of Progetto IRNERIO
DOI: http://doi.org/10.6092/issn.2532-8816/11187


   Development of an ontology for modelling medieval
      manuscripts: the case of Progetto IRNERIO

                     1
                      Sebastian Barzaghi, 2Monica Palmirani, 3Silvio Peroni

                                   1,2,3
                                          University of Bologna, Italy
                                      1
                                       sebastian.barzaghi2@unibo.it
                                       2
                                         monica.palmirani@unibo.it
                                          3
                                            silvio.peroni@unibo.it


       Abstract

The catalogue of digitized medieval texts managed by Progetto IRNERIO contains a rich
amount of legal, cultural and historical data that is neither easy to access nor linked to relevant
external information. This paper introduces an ontology, called Medieval Manuscripts
Ontology (MeMO), to model these texts so as to allow researchers to represent, identify,
analyse and retrieve the information within and related to them. MeMO has been designed
with a solid methodology in order to be compliant with the requirements of the domain
experts (the preservation of the historical narrative, the representation of the context and the
description of the collection). Also, it is flexible and richly documented so as to be easily
reusable and extensible for further expansions. Thus MeMO allows one to model the resources
managed by Progetto IRNERIO with precise semantics so as to avoid information loss and to
support a better representation of the conceptual complexities that characterize the collection.
Il catalogo digitale di manoscritti medievali gestito dal Progetto IRNERIO è ricco di materiale
di interesse legale, culturale e storico difficilmente accessibile e separato rispetto a contenuti
esterni ad esso rilevanti. Questo articolo introduce un'ontologia chiamata Medieval
Manuscripts Ontology (MeMO) e sviluppata per modellare questi manoscritti in modo da
permettere agli studiosi di rappresentare, identificare, analizzare ed estrarre le informazioni in
essi contenute. MeMO è stata sviluppata seguendo una metodologia robusta e agile, in modo
da rispettare i requisiti richiesti dall'esperto di dominio (la preservazione della narrazione
storica, la rappresentazione del contesto e la descrizione della collezione dei testi). MeMO,
inoltre, è flessibile e riccamente documentata in modo da essere facilmente riusabile e
estendibile in possibili scenari futuri. Quindi MeMO permette di modellare le risorse del
Progetto IRNERIO con termini precisi per evitare una perdita di informazioni e supportare
una miglior rappresentazione delle complessità concettuali che caratterizzano la collezione.




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     Umanistica Digitale - ISSN:2532-8816 - n.9, 2020


       Introduction

The Royal College of Spain in Bologna (http://www.realecollegiospagna.it/) hosts the
prestigious collection of medieval texts on Roman and Canon Law that has been carried out,
since the XII century, by jurists and law scholars hailing from every part of the continent and
operating in Bologna, Italy. This work includes important information of legal, cultural and
historical nature, which dates to the period of time between the X-XI centuries to the
beginning of the XVI century.
Due to the varied fields of study involved in its history, the collection is extremely rich and
heterogeneous in terms of nature, provenance and expected use. The subjects range greatly,
from legal documentation to philosophical and theological dissertations. Next to illuminated
manuscripts there are texts supplemented by marginalia, bare volumes for scholastic use, letters,
and other types of ancient writings made on parchment or paper. Many codices also collect a
notable quantity of different manuscripts, whose text is summarized and enriched by intricate
apparatuses of glosses. These volumes, manuscripts, annotations, illustrations and their
descriptions attract jurists, historians, theologians, codicologists and other types of scholars due
to their content, their features and the historical context in which they thrive. For example, the
real value of a page in a codex often lies within the glosses, the comments made in later times
by different scholars, that are clearly separated from the original text. Text, glosses, metadata
and other commentaries, layered on the top of each other, form a scientific and historical
narrative which has been weaved by multiple different agents through the centuries.
A work of digitization of the collection, led by the publishing house CLUEB (https://clueb.it/)
and consisting in the complete scanning of all of the codices from beginning to end, allowed
these documents to be available for remote consultation and documentation, thus increasing
public accessibility to the collection. Such digital reproductions (more than 138.000) have been
published       on      a    digital     catalogue      managed      by     Progetto   IRNERIO
(http://irnerio.cirsfid.unibo.it/), a project maintained by the Interdepartmental Centre for
Research in History, Philosophy and Sociology of Law and in Computer Science and Law
(CIRSFID, http://www.cirsfid.unibo.it/) at the University of Bologna.
The infrastructure of the digital catalogue is based on the TEI P5 ENRICH schema
(http://projects.oucs.ox.ac.uk/ENRICH/), which provides a complete, integrated framework to
encode, catalogue and describe the manuscripts and their digital images, as well as their
descriptive material, text and metadata. However, the way such information is currently
rendered lacks the depth of representation that is required to model effectively the peculiarities
of this collection. For example, direct answers to queries pointed to the data itself cannot be
provided in a clear and straightforward way. Despite the abundance of material and the
availability of structured data that accompanies the manuscripts, there are only a few access
points to it in the catalogue such as the author’s name, the title of the manuscript or the time
period related to the codex. In addition, the current structure of the records does not provide
links to relevant information found in external resources (e.g. bibliographic citations to critical
editions). This presents certain problems for the user who is not familiar with the content of a
specific codex, a manuscript, the description or the identity of a certain author responsible for


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                                                      manuscripts: the case of Progetto IRNERIO

the realization of a manuscript or a gloss. Moreover, the descriptors employed by TEI
ENRICH, albeit useful, are not enough. TEI-based analytic descriptions of the physical and
intellectual contents of this kind of resources, as well as digital images obtained from a process
of digital scanning, function as digital surrogates of these artefacts to further support scholarly
research. Nonetheless, these materials are often assembled together with little regard for existing
complementary resources, leaving it to the end-user to make and sustain the connections across
collections, that remain fundamentally siloed, with no way to establish permanent semantic
connections of their contents [4].
Another fundamental issue in using TEI is the segmentation it operates on the descriptive and
scientific narrative of the text. The structure and the content of historical manuscripts – such as
those that are part of the catalogue of Progetto IRNERIO – are held together by a scholarly
description that is usually tied to multiple factors (e.g. historical context, legal discourse,
additional annotation layered through time, etc.) and prone to the overlapping problem [22].
Manuscripts do not exist as isolated entities: they are part of a larger story that builds on their
collections, layering of annotations, authors’ names variations, and so on [35]. An alternative
data model that is capable of handling and expressing such level of complexity is thus needed.
As highlighted in past works, e.g. [1], problems related to data integration, knowledge
formalization, information retrieval and mapping can be addressed and solved by Semantic
Web technologies. A Web of data would allow humanities researchers to apply these
technologies to retrieve adequate answers to multiple different kinds of research topics [2] and
to use them as a safeguard to guarantee interoperability, usefulness, openness, dissemination,
communication, sharing and integration of the data and metadata of collections on the Web
[23].
One of the main aspects that characterises the Semantic Web is the notion of Web ontologies, a
way to encode a data model to share knowledge on the Web, which comprises a set of concepts,
their definitions and a series of semantic interrelationships between them [37].1
There are important benefits from using ontologies. Auer and Herre [3] argue that ontologies
capture the semantics of the knowledge in a format that is designed to be easy to maintain and
efficient to process by reasoning algorithms. The organization of knowledge and the knowledge
itself about the modelled objects are expressed in a clear, meaningful and documented way, for
both human and software agents, and the information becomes inferable, reusable and
accessible to scientific communities, researchers, companies and general public. Finally, using
an ontology entices new means of scholar inquiry, such as to operate searches on implicit
information based on automatic reasoning or to link a resource to multiple other resources
existing on the Web. Overall, ontological data modelling can be used as a method for
organizing discrete facts into a coherent information system where semantic information is
structured, managed and made available to a larger portion of target users.
This article presents the Medieval Manuscripts Ontology (MeMO). MeMO is an OWL 2 DL

1   See [15] for an overview on the history of the term ‘ontology’ and its usage in both philosophy and
    computer science.

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ontology that has been developed for modelling in a formal way the body of knowledge related
to the collection of medieval texts of the Royal College of Spain in Bologna, Italy, which has
been digitised within Progetto IRNERIO. The goal was to provide a data model that enables:
    •    the preservation of the flow of historical narrative and the layering of information
         provided by different agents through the course of time;
    •    the representation of the context of the manuscripts, i.e. the correlations between the
         material in the collection and the other entities that contribute to shaping its
         informational context;
    •    the description of the structure of the material, from both a physical and a conceptual
         point of view, in its particular components and features.
In order to address the needs listed above, the development of MeMO was based on a thorough
analysis of the manuscripts catalogue and on existing, well-founded models such as the
Functional Requirements for Bibliographic Records (FRBR) [18], the Semantic Publishing and
Referencing Ontologies (SPAR) [32] and Ontology Design Patterns (ODP) [12].
The rest of the article is structured as follows. Related works provides a review of some of the
most important works about ontology modelling in the domain of manuscript studies.
Methodology tracks the workflow of the process through which MeMO has been designed and
developed. The Medieval Manuscripts Ontology provides a high-level description of MeMO,
while Example of use shows how it can be used within the body of knowledge included in the
digital catalogue of the Progetto IRNERIO. Current status describes the current status of the
implementation of MeMO, highlighting the main scenarios that have been handled.
Conclusions concludes the paper and proposes some further developments.


        Related works

In the last two decades, several projects have been carried out in order to develop an ontological
model of the world of discourse related to manuscript texts. Being a formalized interpretation
of reality, an ontological model may be developed through a few different approaches, each
with its own advantages and disadvantages. With regard to the Digital Humanities, a
fundamental difference has emerged between two different modelling approaches: a document-
centric approach and an event-centric approach. To date, most of these projects have relied on
global, high-level models, such as the CIDOC Conceptual Reference Model (CIDOC-CRM)
[8]. Other models, based on a document-centric approach to describe manuscript information,
have been reused as well, although to a lesser extent.
The document-centric approach has been employed by Dröge et al. [10] in Digitised
Manuscripts to Europeana (DM2E), a project born with the objective to represent metadata in
the domain of handwritten manuscripts. DM2E specializes the Europeana Data Model (EDM)
[19], a generic representation of the semantics in the cultural heritage domain, for the domain
of manuscripts. The main objective of the project is to create a model tailored on the data


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                                                      manuscripts: the case of Progetto IRNERIO

providers’ needs and that would enable rich semantic mappings of the provided data through
the reuse of other ontologies like the DCMI Metadata Terms (DCTerms), the Bibliographic
Ontology (BIBO), the FRBR-aligned Bibliographic Ontology (FaBiO) [30] and the Open
Archives Initiative Object Reuse and Exchange vocabulary (OAI-ORE).
The majority of the existing ontological schemes for historical manuscript representation,
however, embrace an event-centric approach, which focuses on developing fundamental
ontological models to provide a more complete semantic representation of the object [17],
which is understood as an entity whose ontological status heavily depends on its contextual
information. Given their vast descriptive breadth, event-centric ontologies have been also
employed to resolve data integration problem, an issue of gaining interoperability among
heterogeneous schemata, formats and metadata which has emerged as an effect of unresolved
semantic problems and proliferation of different mappings.
Vieira and Ciula [38] developed an ontology (FRH3) to model the information contained in
the Fine Rolls of Henry III. The Fine Rolls are historical documents that record monetary
transfers done to the king of England by municipal and religious individuals or corporate
bodies in exchange of concessions and favours of social, political and economic nature. One of
the main goals of the project is to produce richer indices and search mechanisms to help
researchers in the retrieval and interpretation of the source material. The approach they use is
to extract data from TEI-XML files, each representing a roll which was marked up as to include
structural information, temporal information and semantic content, and to plot them into an
ontological model constructed by reusing CIDOC-CRM and other ontologies such as
DCTerms, WGS84 Geo Positioning (GEO), Simple Knowledge Organization System (SKOS)
and the Time ontology (TIME) [16].
Similar work has been pursued by others as well. The objective of the Sharing Ancient WisdomS
project (SAWS) [20] has been to create a model to capture the knowledge contained inside
TEI-annotated manuscripts related to Greek and Arabic ancient wisdom literature. The main
objective of SAWS is to represent, identify and analyse this flow of knowledge across these
texts, as well as the evolution patterns of these sayings within their cultural contexts, and to
facilitate the process of sharing research work and publishing digital editions of the material.
The relationships within SAWS manuscripts have been encapsulated within an ontological
model which formally defines the vocabulary being used to express the RDF information. In
developing the model, the FRBR2 object-oriented model (FRBRoo) [36] has been reused as the
base ontology to express relationships among the texts, the excerpts of the texts and analogous
bodies of material. Other ontologies reused by SAWS are CRM Digital (CRMdig) [9], BIBO,
SKOS and DCTerms.
Biblissima [14] is one of the first attempts to use Semantic Web technologies for modelling


2   The Functional Requirements for Bibliographic Records standard (FRBR) [18] is a model for
    describing bibliographic resources proposed by IFLA (https://www.ifla.org/publications/functional-
    requirements-for-bibliographic-records). FRBRoo is an ontology based on both CIDOC-CRM and
    FRBR, and expressed in RDF Schema (RDFS).

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descriptions of manuscripts. It focuses on the management of the information related to a huge
and complex mass of documentation on manuscripts and early printed books, dated from the
8th to 18th centuries. The majority of Biblissima databases contain descriptive and structural
metadata for medieval manuscripts, but the project also includes digital editions in TEI-XML
format. In order to handle the heterogeneity of formats and data, it uses a mixture of CIDOC-
CRM and FRBRoo as a common framework to facilitate internal mapping and allow other
people to expose their data in RDF, in compliance to a globally established standard. The
ontology also exploits a thesaurus based on technical terms and descriptors that are commonly
used for indexing medieval resources. In addition, the project's data on people, corporate
bodies, places and titles have been aligned with existing authority lists, such as the Virtual
International Authority File (VIAF) and GeoNames (GN). By adopting open standards for
both the ontology and the thesaurus, the data might also be aggregated and used in other
projects.
Zhitomirsky-Geffet and Prebor [39] provide a review of recent techniques and present a
comparison against earlier methods, such as DM2E and FRH3. In their paper they propose to
design an ontological model to represent the narrative of historical handwritten Hebrew
manuscripts, in order to enable a systematic research of the knowledge embedded into them.
The underlying approach they took consisted in treating manuscripts as ‘living entities’, with a
life cycle based on events, and in developing a data model to describe such life cycle
accordingly. In order to explicitly provide an adequate semantic data representation of the
manuscript and its biography, they use an event-centric ontological model which was built as
an extension to existing ontologies such as CIDOC-CRM, FRBRoo, DM2E, SKOS, BIBO,
the Citation Typing Ontology (CiTO) [30], DCTerms, the Friend Of A Friend vocabulary
(FOAF) [6], the Biographical Information vocabulary (BIO), the EAC-CPF Descriptions
Ontology for Linked Archival Data (EAC-CPF), the VIVO Core Ontology (VIVO), the
Linking Open Descriptions of Events ontology (LODE) and the SEM Ontology (SEM).
In order to capture the specific semantics needed to represent the resources in the digital
catalogue of Progetto IRNERIO without compromising on either precision or practicability (or
both), great care must be taken with the development of the model from at least two points of
view. On the one hand, the model should be able to deal with all the three complexities of
representing manuscripts mentioned in the introduction – i.e. preservation of the flow of
historical narrative, representation of the context of the manuscripts, and description of the
structure of the material. On the other hand, it should prove to be adequate for pragmatic uses
within an existing digital catalogue implemented by means of specific technologies.
From this perspective, ontologies that are heavily based on either CIDOC-CRM or other
models emanated from it (e.g. FRBRoo), such as FRH3, SAWS, Biblissima, and Zhitomirsky-
Geffet and Prebor’s model, would not be a good fit for the project. CIDOC-CRM, albeit being
an ontology specifically developed for cultural objects, provides only primitives with high-level
semantics that inevitably abstract them from any concrete implementation. According to
Nussbaumer and Haslhofer [28], this is due to the fact that it has been developed as a global
ontology with the objective to provide a generalized framework according to which it is
possible to operate decentralized data integration between different metadata schemas, thus


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resulting, more often than not, into similar entities and relations being mapped into different
ontological chains or, vice versa, different entities and relations being mapped to identical
chains. The double bond between high-level semantics and lack of implementation guidelines
implies the need to add more information from controlled vocabularies to disambiguate a
model that was already tortuous to begin with. This causes CIDOC-CRM to be over-
engineered, too difficult to comprehend and to be used successfully with respect to this case
study, which instead is related to a precise project with its very specific needs and users – which
may not necessarily be practical of the nomenclature and structure imposed by CIDOC-CRM.
By contrast, the Functional Requirements for Bibliographic Records standard (FRBR) [18], a
well-known and robust model proposed by the International Federation of Library Association
(IFLA) for representing bibliographic resources and metadata, would be a good basis to build
on due to its flexibility in representing complex and layered objects. In addition, some of the
SPAR Ontologies such as FaBiO and CiTO, by explicitly focusing on documents and their
description in FRBR terms, can further expand the possibilities offered by FRBR through the
definition of additional bibliographic entities and the relations between them. Finally, certain
conceptual issues that might entail significant cognitive effort in their modelling (such as
recording changes in values through time) can be easily dealt with by plugging Ontology
Design Patterns (ODP)3 into other models. For example, Time Interval (TI) [13] is an ODP
which enables an intuitive description of periods of time. TI, in turn, is reused by other
convenient ODPs such as Time-indexed Value in Context (TVC) [34], useful to describe
situations in which entities have values during a certain time interval and within a particular
context, and Literal Reification [13], which allows modelling certain literals as individuals of a
class so that one may use them as proper subjects or objects of RDF statements within an
ontology.


       Methodology

This section explains in detail the methodology we used to develop MeMO. In Preliminary
metadata analysis, the inquiry carried out on the catalogue of Progetto IRNERIO is described
to detail how and which metadata have been drawn from it. In Ontology design and
development, the reused ontologies and some other additional tools are presented to provide a
complete overview on the ontology development process.


       Preliminary metadata analysis
The objective of the analysis was to determine an initial set of primitives (classes, attributes and
properties), originally encoded into the catalogue records as metadata, which could then be
used as a basis to develop the ontology. To this end, the work on the catalogue focused on
identifying different types of fields in the catalogue records and their decomposition into

3 ODPs are small, documented and reusable ontologies that can be used as modelling components in
ontology design and engineering [12].

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atomic ontological units.
The single codex record provides a description of all the available information and metadata
from the catalogue about the codex (such as materials, dimensions, etc.), a list of the
manuscripts it contains, a bibliography and a list of unnumbered elements such as flyleaves,
plates and covers, also belonging to the codex. A codex can be incomplete, with a number of
missing folios from it. Neither title nor authorship are provided, so each codex is organized
according to a specific identifier made up by either a combination of three numbers, ranging
from 000 to 286, or a letter, ranging from A to P in alphabetical order (with the exception of
the letters D, E, M, N and O).
The single manuscript record provides access to the sequence of images of the digitized folios, a
set of metadata (e.g. title, author, editions, etc.) and to a list of related manuscripts contained in
the same codex. In the collection there are more than 800 registered authors, and often, beside
their name, each author has one nickname or even multiple variations of name. More often
than not, there is also a misalignment between the identity of an author of a manuscript and
the identity of the glossators who commented on such manuscript.
The metadata have been categorized in terms of their complexity with respect to the
information they describe, while using the metadata schema of the catalogue as a guiding tool
and a yardstick for evaluating the consistency of certain metadata.
Identifier, materials and title can be converted into ontological elements with relative ease.
other metadata cover different types of data (e.g. description, century). The description field
contains a broad array of miscellaneous information which can be gathered under several
distinct metadata, such as style of script, decorations, alternative identifiers, and so on. The
century metadata describes temporal information as well as spatial indications of some sort (i.e.
a place), thus recording two very different things. Other metadata present inconsistent or
unclear information (e.g. author, dimension, columns). There are many inconsistencies between
the identity of the author of the manuscript and that of the glossators. The dimensions metadata
describe the size of the codex and (possibly) the size of the folios, but the attribution of size to a
codex is problematic in terms of conceptualization, since it technically refers to the size of the
binding of that codex4. In addition, many metadata express meaningful relationships between
the data contained in the catalogue that need further explanation (e.g. foliation, works,
bibliography, edition, nickname, name, citation, incipit, explicit, notes, and so on).


        Ontology design and development
This subsection presents the methodology used for developing the ontology, along with a list of
reused ontologies and a series of supporting applications used during the development process.
SAMOD. The Simplified Agile Methodology for Ontology Development (SAMOD) [29] is
an agile methodology for developing ontologies that is partially inspired to the Test-Driven
Development process in software engineering and other existing agile ontology development

4 This point is actually addressed in the TEI Guidelines. The <dimensions> element has attribute @type,
which can have "binding" or "leaf" as a value (among others), but not "codex".


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methodologies, such as eXtreme Design (XD) [5]. As shown in Figure 1, SAMOD consists in
an iterative process made up by three main phases: 1) the development of a modelet formalizing
a scenario that belongs to the domain of discourse, and the creation of a test case comprising the
modelet and a series of additional resources such as glossaries, diagrams and query examples; 2)
the merging of the modelet to the current model, developed in the previous iteration (if any);
3) the refactoring of the new current model resulting from the previous step. Before moving on
to the next step, each test case must pass a testing phase made up by a model test, a data test
and a query test. Each step of the methodology ends with the formal implementation of the
ontology in its current state, called ‘milestone’, accompanied by all the previous test cases,
updated accordingly.




Figure 1: A summary of the three steps of SAMOD.


With respect to the project scope and the domain expert’s needs, SAMOD has proven to be
extremely beneficial as a methodology for ontology development, since it allows one single
person to build up – within a reasonable period of time – a well-developed, documented,
reusable ontology by using exemplars of data and testing phases. In this way, the ontology turns
out to be both compliant with the domain expert’s specific demands and easily embeddable
with other models so as to be extendable to a more precise description of the domain through
further iterations.
Reused ontologies. In the third step of every iteration, SAMOD suggests importing other
models into the ontology whenever possible, in order to maximize the ontology reusability in
other contexts. FaBiO – being an ontology focused on entities that are textual in nature, and/or
referred to by bibliographic references – has been reused as the basis on which MeMO was
built. It defines its own set of entities (that are subclasses of the original FRBR entities) by
reusing a well-known RDF vocabulary (FRBRcore) that incorporates the basic concepts and


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relations of the FRBR model. CiTO was used to model the numerous references existing
between glosses, manuscripts, codices, metadata, and other relevant entities that are part of the
collection (e.g. a gloss citing another gloss in a given manuscript). Literal Reification was used
to record how certain elements, normally modelled as literal strings, might change over time
(e.g. the name of an author), while TVC was used as a basis to model certain metadata related
to a manuscript and the way they might change over time on the basis of their textual context
and their role within it (metadata referring to the incipit of the manuscript, for example). TI
was used in conjunction with Literal Reification and TVC to express the concept of time
interval. Finally, DCTerms and FOAF were used for modelling date times, names, titles, and so
on.
Supporting tools. A series of supporting applications have been used during the development
process:
    •    the Live OWL Documentation Environment (LODE) [33] is an open source service
         that automatically extracts classes, object properties, data properties, named
         individuals, annotation properties, general axioms and namespace declarations from
         an OWL ontology, and renders them as ordered lists, together with their textual
         definitions, in a human-readable HTML page designed for browsing and navigation;
    •    the Graphical Framework for OWL Ontologies (Graffoo) [11] is an open source tool
         that can be used to present the classes, object properties, data properties, individuals,
         general axioms, namespace declarations and restrictions within OWL ontologies as
         user-friendly diagrams;
    •    Protégé [27] is an open-source ontology editor developed at Stanford University
         which provides a graphic user interface, deductive classifiers and OWL 2 DL
         reasoning engines (e.g. HermiT and Pellet) to validate the consistency of an ontology
         and to infer new knowledge from it;
    •    Apache Jena Fuseki is a SPARQL 1.1 server with a web interface, backed by the
         Apache Jena TBD RDF triple store, which provides the SPARQL 1.1 protocols for
         query and update as well as the SPARQL Graph Store protocol.
During the development of MeMO, both LODE and Graffoo proved to be stable tools with a
good level of usability. LODE has been used to produce the HTML documentation of the
ontology by extracting the labels, comments and provenance information of the ontology
elements. Instead, Graffoo has been used to create the diagrams of the various modelets, the
refactored models and the full ontology. Protégé, arguably the most widely used open source
software for building and maintaining ontologies [24], has been used multiple times in each
iteration for testing the consistency of the modelet and the dataset, the merged model, and the
refactored model. Although it is not the best solution in terms of query execution time [25],
Fuseki can be quite useful for easy, quick testing [26]. In particular, it has been used in each
iteration of SAMOD as a query engine for testing the correctness of the formal competency
questions and for addressing the particular requirements they expressed.



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       The Medieval Manuscripts Ontology

The Medieval Manuscripts Ontology (MeMO) is an OWL 2 DL ontology that aims at
providing a framework for the formal description of the digital catalogue of medieval texts
managed by Progetto IRNERIO. MeMO has been made available with a Creative Commons
Attribution License 4.0.
The Graffoo diagram in Figure 2 visualizes the current version of MeMO. The prefixes and
relative base URIs of the models which MeMO reuses are listed in Table 1.




Figure 2: The Graffoo diagram of MeMO.




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The resources described by the catalogue of Progetto IRNERIO are artefacts characterized by
multiple levels of complexity: non-immediate compositionality, references to both internal and
external resources, variability of authorship identity, historical layered commentaries, and so on.
In order to adequately represent such complexity, MeMO has been designed around FRBR,
which describes bibliographic resources from four different conceptual points of view that are
interliked with each other and are defined by the categories of Work, Expression, Manifestation,
and Item.5
FRBR allows one to have a holistic perspective about the resource, on multiple levels of
conceptualization, by breaking down the semantic and conceptual ambiguities related to
objects into different but related and layered concepts, and by allowing the description of an
artefact and its relations with other entities to be more expressive, precise and dynamic.
Nonetheless, FRBR has some limitations. Even though the definitions of its concepts are quite
straightforward, FRBR is not easily understood by the common user, who finds the terms
Work, Expression, Manifestation and Item quite ambiguous. According to FRBR, any object
(such as a manuscript, for example) has to be described by taking into consideration all the four
levels at the same time, in order to have a complete view over it. This multi-layered
conceptualization is difficult for an average user to comprehend, because it is much more
intuitive to expect the concept of that object to exist at a single FRBR level. In order to avoid
this issue without giving up the expressiveness of FRBR, a good solution is to place that object
at the level that is deemed more appropriate in relation to the scenario taken into
consideration.

           Prefix                                      Base URI

           memo                                        https://w3id.org/irnerio/ontology/m
                                                       emo/

           cito                                        http://purl.org/spar/cito/

           dc                                          http://purl.org/dc/elements/1.1/

           dcterms                                     http://purl.org/dc/terms/

           fabio                                       http://purl.org/spar/fabio/

           foaf                                        http://xmlns.com/foaf/0.1/



5   A FRBR Work is the high-level description of the essence of a particular resource, which does not
    depend on any concrete representation. It is realized through one or more Expressions. A FRBR
    Expression is the form taken by a Work when it is realized in terms of content. It is the realization of
    one and only one Work and is embodied in one or more Manifestations. A FRBR Manifestation is a
    particular embodiment in the physical world of an Expression, according to a specific format. It
    embodies one or more Expressions and is exemplified by one or more Items. A FRBR Item is the
    single, tangible, and located exemplar of a certain Manifestation. It exemplifies one and only one
    Manifestation.


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          Prefix                                  Base URI

          frbr                                    http://purl.org/vocab/frbr/core#

          literal                                 http://www.essepuntato.it/2010/06/l
                                                  iteralreification/

          owl                                     http://www.w3.org/2002/07/owl#

          rdf                                     http://www.w3.org/1999/02/22-rdf-
                                                  syntax-ns#

          rdfs                                    http://www.w3.org/2000/01/rdf-
                                                  schema#

          ti                                      http://www.ontologydesignpatterns.
                                                  org/cp/owl/timeinterval.owl#

          tvc                                     http://purl.org/spar/tvc/

          xsd                                     http://www.w3.org/2001/XMLSche
                                                  ma#

        Table 1: The prefixes and the corresponding base URIs of the models reused in MeMO.

For example, this approach has been used systematically for developing FaBiO, which is the
main reason why we decided to use it as a foundation for MeMO. In order to embrace this
approach and be consistent with the scenarios that are present in the case study, MeMO reuses
FaBiO interpretations of FRBR entities as super classes of its entities. In particular: manuscript,
text and gloss are conceptualized as subclasses of fabio:Expression (since they carry a
content and are not inherently related to a precise format), while codex and folio are
conceptualized as subclasses of fabio:Manifestation, since they carry a format that
functions as a container for both text and glosses, and thus for manuscripts as well.
A manuscript (represented by the class memo:Manuscript) is a handwritten composition
made up by one text (the primary text of a manuscript, represented by the class memo:Text)
and zero or more glosses (marginal annotations, represented by the class memo:Gloss). A
codex (represented by the class memo:Codex) is a set of one or more folios, in which one or
more manuscripts are embodied. The MeMO understanding of the term ‘codex’ refers to a
physical object that should not be confused with ‘the Codex’ (i.e. the Codex Justinianeus), nor
with the concept of manuscript (classically understood as a physical document written by hand
by someone). Instead, a codex is a composite entity, without a clear authorship and title, that
embodies manuscripts. A folio (a leaf or sheet of paper or another material, represented by the
class memo:Folio) is a physical object that is usually – but not necessarily – part of a codex.
It is made up of two sides, one called recto (the front side of a folio) and the other called verso
(the back side of a folio). It carries a specific format and layout. According to how MeMO has


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been designed, text and glosses of a manuscript attain a physical realization in the moment they
are embodied in the physical format carried by a folio. In this way, it is possible to represent
many different scenarios that are effectively present in the collection of Progetto IRNERIO
(e.g. multiples manuscript in the same folio, non-sequential foliation, bilocation of the same
manuscript in two codices, etc.) without incurring in logical inconsistencies.


        Example of use

As aforementioned in the introduction, MeMO has been developed first and foremost with the
objective of addressing the requirements of the domain experts – namely jurists, historians,
theologians, codicologists, and other scholars – interested in the collection. In this subsection
we illustrate one of the possible applications of MeMO within the digital catalogue of the
Progetto IRNERIO.
In particular, glosses and citations play a fundamental role in the description and study of the
resources of Progetto IRNERIO.6 Explanatory glosses of various kinds occur frequently in
manuscripts, especially in those with biblical or legal content, as sophisticated tools for
studying, recovering, restoring and producing new knowledge on the basis of existing work,
like the medieval glossators from the juridical school of Bologna did with the mass of Justinian
legislation [21]. Glossators from Bologna managed to construct an increasingly large apparatus
of glosses which layered up on each other in the form of observations, references, links and
comments. Through some of these glosses, they effectively created fully-fledged authoritative
standards of reference for avoiding contradictions between statutes and for determining the
constitutionality of certain legal stipulations. Historians of law might be interested in the
glosses and other forms of commentary that take place in the margins of the page, because the
explanatory comments and annotations that medieval manuscripts hoarded over the centuries
can present the scholars with a living record of use, study and reference of that resource. A
medievalist’s research might be centered around the reconstruction of the network of references
between a manuscript text and a series of glosses. A modern historian might focus on the way
glosses and other resources (such as textual metadata) comment on other glosses, thus
spreading the volume of commentaries beyond the collection itself. A contemporary historian
might be interested in retracing how a certain manuscript has been cited by critical editions
over the course of time.
Overall, MeMO allows to easily represent such articulated data and to compute the level of
annotation of each gloss, changing dynamically the perspective on a certain source and
inferring new information. In order to demonstrate this, an example of use of MeMO, related
to glosses and citations, is discussed below. The example is based on test data, encoded in


6   In our context, a citation is defined as ‘a conceptual directional link from a citing entity to a cited
    entity, for the purpose of acknowledging or ascribing credit for the contribution made by the
    author(s) of the cited entity. The citing and cited entities may be scholarly publications, online
    documents, blog posts, datasets, or any other authored entities capable of giving or receiving
    citations.’ [31].


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Turtle, a RDF serialization that allows one to write RDF statements in a form that is intuitive
and compact, with the possibility of concatenating prefixes with base URIs in order to
abbreviate them into prefixed names. All the entities that refer to the test data have a specific
base URI (https://w3id.org/irnerio/data/memo/) abbreviated through the prefix ex. These
Turtle sources are publicly available on the GitHub repository https://github.com/irnerio-
opendata/memo, in the data directory.7 In particular, the following scenario is expressed in
Turtle as shown in Text 1.
A manuscript (ex:manuscript_1) is made up by a text (ex:text_1) and six glosses
(ex:gloss_a, ex:gloss_b, ex:gloss_c, ex:gloss_d, ex:gloss_e,
ex:gloss_f). These entities are related to each other through a series of relationships,
which build up a complex record of interpretations, commentaries and references. In fact,
glosses made by different people in different time periods layer on the top of each other, either
citing or annotating or referring to the text, or another gloss, or a whole manuscript. These
relationships are indicated by a series of properties. 8 The property dcterms:relation
represents the most general way in which an entity can address another entity. Its subproperty
memo:annotates indicates that some entity provides a critical or explanatory observation
to another entity. The property cito:cites, defined in CiTO and aligned as a subclass of
dcterms:relation, expresses the fact that a citing entity references a cited entity. In this
way, it becomes possible to infer the annotation level of a gloss and how it varies in relation to
other entities.
A scholar might be interested in the glosses that are part of the manuscript and cite its text, or
in the second-level glosses that are part of the manuscript and cite or annotate its text, or that
annotate or refer to another gloss, such as ex:gloss_a.




7   For the prefixes used to abbreviate the base URIs of the ontologies, please refer to Table 1.
8   When developing MeMO, domain and range constraints of these properties have not been defined so
    as to allow an easy integration with other models and augment the model extensibility in addition to
    what has already been defined, thus allowing the further addition of other types of properties in the
    future.

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ex:manuscript_1 a memo:Manuscript ;
          frbr:part ex:text_1 , ex:gloss_a , ex:gloss_b , ex:gloss_c ,
          ex:gloss_d           , ex:gloss_e , ex:gloss_f .
ex:gloss_a a memo:Gloss ;
          cito:cites ex:text_1 .
ex:gloss_b a memo:Gloss ;
          dcterms:relation ex:text_1 .
ex:gloss_c a memo:Gloss ;
          memo:annotates ex:gloss_a .
ex:gloss_d a memo:Gloss ;
          dcterms:relation ex:gloss_a .
ex:gloss_e a memo:Gloss ;
          memo:annotates ex:gloss_b , ex:gloss_c .
ex:gloss_f a memo:Gloss ;
          cito:cites ex:text_1 ;
dcterms:relation ex:gloss_d ;
          memo:annotates ex:gloss_e .
ex:text_1 a memo:Text .

Text 1: Turtle code representing the relations between a manuscript, its text and a set of glosses that are
part of it.

Due to the way MeMO has been modelled, it becomes quite easy to navigate this network in a
way that allows the desired glosses to be returned according to a level of annotation that shifts
dynamically with the scholar’s perspective on the source. The level of annotation can be
computed according to different types of relationship between a memo:Gloss and another
entity (e.g. memo:Manuscript, memo:Text, memo:Gloss) by counting the property
edges of one or more types of relationship. This is addressed in SPARQL queries through the
use of property paths. Property paths are a way of expressing chains of properties (forward and
backward) without the need to bind all the individual resources along the way, which is
especially important if a variable number of edges are to be allowed. The path language for
SPARQL property paths is described in Section 9.1 ‘Property Path Syntax’ of the SPARQL 1.1
Query Language Recommendation.
Text 2 shows an example of a simple SPARQL query that exploits property paths to navigate
the network of references between glosses. The query returns all the second-level glosses that are
part of ex:manuscript_1 and annotate or cite ex:text_1.




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                                                      manuscripts: the case of Progetto IRNERIO

SELECT ?gloss
WHERE {
          ?gloss a memo:Gloss ;
          frbr:partOf ex:manuscript_1 ;
          (memo:annotates|cito:cites) / (memo:annotates|cito:cites) ex:text_1
}

Text 2: A SPARQL query which returns all the second level glosses that are part of a specific manuscript
and annotate or cite its text.
The two occurrences of(memo:annotates|cito:cites)represent two elements of the
property path (each counting as one level of annotation) that are sequenced one after the other,
from left to right, through the use of a slash (/), which in the property path syntax serves as a
sequencing operator. Each path element consists of a combination of two object properties
memo:annotates and cito:cites enclosed together in brackets and separated from
each other by a vertical bar (|), which in the property path syntax indicates an alternative path
of one property or the other. The sequencing of grouped alternative properties allows one to
test the existence of the desired path between any gloss and the text ex:text_1 by trying all
the alternative paths. As a result, all the glosses which exist at the other end of such paths are
returned (i.e. ex:gloss_c).


        Current status

The development of MeMO has been carried out in six iterations of SAMOD, each resulting
in a model that is responsible for the description of a specific aspect of the domain taken into
consideration.
First iteration: Glosses. The model which was developed by the end of this iteration enables
the description of the gloss apparatus of a manuscript, made of glosses and their relationships
with other entities such as manuscripts, manuscript texts, and other glosses. In particular, a
memo:Manuscript is a handwritten composition that is made up by exactly one memo:Text
and zero or more instances of memo:Gloss. The class memo:Text represents the primary
textual content that is part of a manuscript. Both memo:Text and memo:Manuscript are
subclasses of fabio:Expression. The class memo:Gloss is an annotation that comments
on the manuscript text and accompanies it (as in the margin of the page or between the lines of
the text). memo:Gloss has been modelled as a subclass of fabio:Comment. The object
property frbr:part has been used to describe the part-whole relationship existing between
memo:Manuscript and its parts. The object property memo:hasContent serves as a pointer
to anything that represents the content of another entity. The property dcterms:relation
represents the most general way in which an entity can address another entity. One of its
subproperties, memo:annotates, indicates that some entity makes a critical or explanatory
observation for another entity, while the other ( cito:cites) represents the fact of an entity
citing another entity. It is defined in CiTO and, in the process of being imported to MeMO, it

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has been aligned as a subproperty of dcterms:relation.
Second iteration: Textual metadata. The model developed by the end of this iteration, which
is based on TVC, allows the description of textual metadata associated to a manuscript (e.g.
metadata referring to the incipit, explicit, or final rubric of a manuscript). In particular,
memo:TextualMetadataInTime is a subclass of tvc:ValueInTime and is characterized
by a series of properties. It is related to a manuscript through the object property
memo:hasTextualMetadata,                 a      sub       property     of    tvc:hasValue.
memo:withTextualRole, a subproperty of tvc:withValue, relates a textual metadata in
time with its respective textual role, modelled as a class ( memo:TextualRole) that can
assume the following controlled values: memo:incipit, memo:explicit,
memo:finalRubric. The object property tvc:atTime specifies the particular time interval
that has been associated with the textual metadata by linking it to the ti:TimeInterval
class, which has two data properties that set its start and end dates
(ti:hasIntervalStartDate and ti:hasIntervalEndDate, respectively). The object
property dcterms:creator is used to link memo:TextualMetadataInTime with the
agent       (foaf:Agent)           that      created       it.     The    object   property
memo:relatesToTextualContext relates a memo:TextualMetadataInTime to a
textual context that is, in turn, related to the classes memo:Text and memo:Gloss through
the object property memo:isBasedOn.
Third iteration: Citations. The model developed by the end of this iteration enables the
description of the structure of citations that exists between manuscripts, glosses, textual
metadata, editions and other similar resources. A codex is a set of at least one folio and is
modelled through the class memo:Codex, while folios belong to the class memo:Folio. Both
are subclasses of fabio:Manifestation. The object property frbr:part links the classes
memo:Codex and memo:Folio with each other. A codex and a manuscript are related with
each other through the idea of the manuscript text and glosses being distributed through the
folios that are part of that codex. This situation is modelled in MeMO by using the object
property frbr:embodiment to relate the classes memo:Text and memo:Gloss with
memo:Folio. The model reuses FaBiO for describing certain entities that are external to the
catalogue, such as fabio:Book and fabio:CriticalEdition. Since it deals with
citations, it also leans heavily on the model that has been developed in the first iteration, by
reusing CiTO for representing the citation network existing between the various entities (with
the object property cito:cites) along with other relationships, such as
dcterms:relation and memo:annotates. In addition, critical editions have been
conceptually separated from their realizations in two specific and distinct layers, characterized
by two classes: fabio:CriticalEdition and memo:CriticalEditionVolume. The
fabio:CriticalEdition class is a subclass of fabio:Work and describes the edition
essence, independently from the revisions that can characterize it in time. The
memo:CriticalEditionVolume class is a subclass of fabio:Expression and is used for
pointing to a specific realization of a critical edition. The data property dcterms:title has
been used to model the titles of entities such as fabio:Book and memo:Manuscript.
Fourth iteration: Names. The model developed by the end of this iteration allows one to


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describe of the variations of people’s names in time. It is based on the Literal Reification pattern
in combination with OWL 2 punning and defines a literal:Literal individual that also
belongs to the property foaf:name which has been meta-modelled as a class. Each literal
individual is then assigned a time interval via the dcterms:valid property, whose range has
been appropriately adapted to accommodate the class ti:TimeInterval, so as to represent
the period in which the name is valid. The properties dcterms:creator and
dcterms:created have been used respectively to relate the resources to the person who
created them (represented with foaf:Person) and the dates in which they have been created
by that person (represented with xsd:dateTime).
Fifth iteration: Foliation. The model developed by the end of this iteration enables the
representation of the arrangement of the folios which make up a codex and contain its
manuscripts. In particular, the main structure of the codex, with each part related to the other
through the frbr:part property, is modelled. One or more instances of memo:Folio are
part of memo:Codex, as already anticipated in the third iteration. The classes memo:Recto
and memo:Verso, both subclasses of the class memo:Side, are part of memo:Folio.
Sixth iteration: Codex metadata. The model developed by the end of this iteration allows
describing some features of a codex (e.g. size, materials, number of columns, etc.). The classes
memo:Folio and memo:Binding (which represents the binding of the codex) have been
associated with the class dcterms:PhysicalMedium, which represents the materials of a
folio or a binding, via the property dcterms:medium. The named individuals memo:paper
and memo:parchment are the possible controlled values that dcterms:PhysicalMedium
can take. memo:Folio and memo:Binding are also related to the class
memo:SizeMeasurement, subclass of dcterms:SizeOrDuration, via the property
dcterms:extent. In order to express a size in terms of length, width and with millimeters as
unit of measurement, memo:SizeMeasurement has two data properties called
memo:hasLength              and      memo:hasWidth            and      an     object    property
memo:hasSizeMeasurementUnit that allows it to be associated with the class
memo:SizeMeasurementUnit, a class used to express the concept of measurement unit that
can assume a series of values, according to the unit used, as aptly named individuals. When it
comes to Progetto IRNERIO, all measures are implicitly expressed in millimeters, so the
named individual memo:millimeters is included in the model. For completeness, other
plausible measures have been included in the model through the named individuals
memo:centimeters, memo:decimeters and memo:meters. In addition, the information
related to the number of columns, expressed via the data property
memo:hasNumberOfColumns, is not related directly to a codex; since many types of
variations are possible within the same codex (between ranges of folios, between single folios or
even within the same folio), it has been put in relation with the class memo:Side instead. The
identifier or identifiers of a codex are expressed via the data property dcterms:identifier.
The MeMO GitHub repository contains all the source files of the elements which form the
documentation of the ontology. The development directory contains a folder for each
iteration, thus constituting a full test case with a motivating scenario, a list of informal


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Competency Questions, a glossary of terms, a Graffoo diagram of the model in .png format
(along with its .graphml file), a list of formal Competency Questions written in SPARQL, a
modelet and a dataset (both written in the Turtle RDF serialization).
The data directory contains a set of refactored datasets, one for each iteration, written in the
Turtle RDF serialization. The diagrams directory contains a set of Graffoo diagrams, each
representing the refactored model of its respective iteration. The docs directory contains all
the ontology files and its versions in time. The sparql directory contains a set of refactored
formal Competency Questions.


       Conclusions

This article introduced MeMO, an ontology for modelling the collection of medieval texts and
their catalogue information published and managed by Progetto IRNERIO. MeMO was
designed on the basis of a metadata analysis conducted on the catalogue and was developed by
using SAMOD, a data-centric and pattern-based methodology for ontology development. This
approach allowed to create a fully documented, extendible and dynamic ontological model that
allows to faithfully represent the material in the digital catalogue without excessive conceptual
clutter and with an eye towards potential expansions to cover more information related to the
manuscript studies domain. The methodology proved to be efficient and effective for the task.
The metadata analysis allowed to have a general overview on the material and provided the
researcher with a solid basis on which the ontological model has been built by using SAMOD.
The complexities of the domain and of the collection proved that MeMO is sufficient to meet
the domain expert’s requirements. Still, further work is needed to semantically refine and
expand the model. For example, codex metadata such as Century, Description, and those related
to the style of script, the state of condition, the decoration, and the ruling, need to be
integrated into MeMO in order to take into consideration additional useful information. In
addition, a web service could be implemented to allow users to query and visualize the data
modelled by the ontology.



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