1Archaeology shifts a large part of its field of study towards derived scientific objects, “traces of traces” that were for a long time material (notes, drawings, archives, maps, memoria), and that are now digital or digitized. The HyperThesau project, led by the Archéorient laboratory and financed by the Labex Intelligences des Mondes Urbains of the Université de Lyon, proposes an original approach to the problem of the structural and semantic heterogeneity of these archaeological data: the project intends to found the interoperability of the data on vocabulary and plans to build a thesaurus as a semantic hub for archaeology.
2In the early years of the last decade, the STAR project led by English Heritage produced an extension to the CIDOC Conceptual Reference Model (CIDOC CRM – ISO 21127:2006 standard), which models the archaeological excavation and analysis process (CRM-EH). Following this work, several initiatives and programs (ARIADNE in Europe, MASA in France) have focused their efforts on accessing archaeological datasets and modeling the process of data acquisition in the field with CIDOC-CRM (Tudhope et al., 2013; Doerr et al., 2016). All of these approaches, however, rely ultimately on overcoming mismatches between all possible meanings/representations through the use, below the model, of “controlled” vocabularies (the terms being the concepts of a hierarchical thesaurus) to be aligned with when publishing the data.
3A thesaurus is an organized list of controlled terms. This documentary tool seeks to solve the problem of equivocality in natural language (polysemy and homonymy). A descriptor or preferred term must univocally describe a concept. This type of vocabulary is used for indexing resources and aims to improve documentary researches by increasing the recall rate of relevant documents in relation to a query.
4Strictly defined by the ISO 25964-1 and 25964-2 standards (Hudon, 2012), the structure of a thesaurus allows the expression of all of the semantic relations of a concept (equivalence relation, hierarchical relation, associative relation).
- 1 This work was developed by Emmanuelle Perrin, a specialist in semantic web specially recruited than (...)
5The thesaurus developed as part of the HyperThesau project (https://thesaurus.mom.fr) aims to harmonize the scientific and technical vocabulary of archaeology1. It is built with the multilingual thesaurus manager Opentheso (developed by the Semantic Web and thesauri technological platform of the Maison de l’Orient et de la Méditerranée Jean-Pouilloux) which allows an export in Skos, a standard format for the publication of thesauri in the semantic web. It is mainly based on the collection and processing of terminology used in the databases, resulting from archaeologists’ practices. Nevertheless, it requires a huge amount of work in order to disambiguate terms by means of their definitions, which are attested by various quality sources (Dictionnaire de l’Académie française, Littré, Trésor de la langue française, archaeology manuals, scientific publications, indexes and glossaries) that are systematically referred to.
6At the same time let us consider the disruptive approach of the PeriodO chronological repository (Rabinowitz, 2014, https://perio.do): it aims to organize, not concepts of “periods” in abstracto, but sourced definitions of periods associated with a specific date range and geographic area through identified research work. Taking into account the ambiguity of the ontological status of the “period” (authority or concept), the repository thus constituted allows each person to situate his or her own periodization in relation to all the different definitions that may have been given. The “hub” becomes “a set of stable references of what authorities say about a period, rather than a thesaurus that seeks to impose a consensus on what periods are” (Rabinowitz, 2014). The semantic values of the descriptors that can be harvested are thus often both close and dissimilar. This creative vision of a “controlled vocabulary” is perfectly suitable to the multiple “points of view” that are characteristic of scientific analysis. Transforming this uncertainty into metadata means being able to expand or interpret the semantic and scientific environment of the data, to query it in an uncertain context.
7The path chosen by HyperThesau consists of building a hub thesaurus in order to allow thematic alignments at a fine level, by “bouncing” between perennial repositories, outside the disciplinary community but endowed with the means and authority compatible with their universal vocation, and the multiple vocabularies of archaeologists. This thesaurus prepares the interoperability of archaeological data by providing links with international information systems and those perennial repositories, published in the web of data by the library community (for instance: data.bnf.fr, Library of Congress Subject Heading, VIAF). It is designed as a mediation tool between “local” vocabularies or idiolects and more general documentary vocabularies. With regard to French language, the aim is to make the concepts commonly used in archaeology coexist and communicate with the subject indexing language of the BnF called Rameau (Répertoire d’Autorité-Matière Encyclopédique et Alphabétique Unifié).
8Designed for machine-machine interaction, this thesaurus obeys formal and logical constraints that are very different from scientific interpretation. The strict application of the hierarchical relation as a genus-species relation leads to the “cutting up” of a scientific object into several concepts that will maintain association relations between them. According to the principle of post-coordinated language, the indexing of a bracelet will call upon several descriptors: material, morphology, function, decoration, manufacturing technique, period, places. Similarly, the description of data acquisition associates several branches or sub-domains of the thesaurus: method, field of observation, instrumentation and documents produced. Eventually, alignment with Rameau and Library of Congress subject headings allows interconnection with other datasets through vocabularies and thus allows to enrich the data and produce new knowledge (Perrin et al., 2020).
9The documentarization (method and material used, geographical space prospected, treatments, outputs, etc.) allowing the qualification of the data resulting from geophysical prospecting is, also in that field, a prerequisite for the sharing and the effective reuse of the data sets and/or their representations. This is why a HyperThesau working group, bringing together the Archéorient, Chrono-Environnement and AOrOc French laboratories as well as the Bibracte European Archaeology Center, has been working since 2019 together with a specialist of Digital Humanities, on the creation of a common/consensual geophysical thesaurus (in French at first).
10Based on educational (textbooks, etc.) and scientific material (articles, survey reports, etc.), a list of “candidate” concepts has been structured in a thesaurus, with detailed definitions (from a semantical point of view). The list was then discussed collectively, refined and clarified in depth and finally sourced.
11This level of semantic standardization must be built within such a system of regulated cooperation that associates speakers of the language of the domain (i.e., specialists-experts; in this case, archaeologists-geophysicists), and a knowledge engineer who masters the use of the standard, whose role is not that of arbitrating choices but of being a methodological facilitator of the elaboration of a truly collegial semantics (Bachimont, 2000).
12At the end of 2020, the list has been published in open source on the Internet: https://ark.mom.fr/ark:/76609/arcbvn2dd9cdw (geophysical survey) and https://ark.mom.fr/ark:/76609/arcv63rxnc56x (geophysical data). Each of its concepts has been given a permanent address (URI) to guarantee its citability and reusability. As it stands, the “geophysical prospecting” branch of the HyperThesau thesaurus is an evolving, open and shared resource which, because it is aligned with the major repositories of the semantic web, is available to the entire scientific community to act as a hub for the interoperability of datasets and deliverables from any prospecting campaign (Fig. 1, Fig. 2).
Figure 1. Page of the “Geophysical prospection” concept in HyperThesau thesaurus (Opentheso platform).
Figure 2. Graph of the “Geophysical prospection” concept in HyperThesau thesaurus (Opentheso platform).
13We look forward to work with all our colleagues in order to augment it and reinforce a disciplinary consensus on a shared vocabulary.