The CallFront Ontology

An ontology is a structured, formalized way of describing the concepts within a field of knowledge and the relationships between them, often using a shared and controlled vocabulary. In the digital humanities, ontologies allow heterogeneous data to be described consistently, compared, and connected. CallFront developed its own ontology as a methodological response to the challenges of palaeographic study of Arabic script: a controlled vocabulary makes it possible to describe, in a uniform and interoperable way, scripts that span vast geographical distances and chronological periods, and to make their shared and distinctive features legible to the scientific community.

Where existing standards did not allow these features to be described precisely enough, CallFront also created its own properties, gathered under the prefix cfterms. These properties are declared and documented here. Like the rest of the vocabulary, they are openly published so that they can be examined, cited, and reused beyond the project itself.

Creation of a Shared Vocabulary

One of the aims of the CallFront database was to create a system to describe the essential features of different Arabic scripts originating from a wide range of geographical locations and chronological periods. Most of the scripts showcased in the CallFront project possess no historical written sources theorizing their formal characteristics. The first step in understanding these scripts is to describe and analyze their formal appearance. Calligraphies in the frontiers of the Islamic world present two main streams: calligraphies that are entirely unique and those inspired by the classical canon. We have thus followed a hybrid approach to script analysis drawing on Adam Gacek's work and the calligraphic experience of contemporary calligraphers.

Characters are understood according to various properties such as their position relative to the baseline, the shape of the sections that compose them, the contrast in thickness, the type of serif, or the connections between characters. The language used for the script descriptors is not meant to be an in-depth description but to establish a first layer of description, a layer that will allow the scientific community to explore the common features between the variety of the corpuses here gathered. Each script description begins with the general structure of the composition, then analyzes spacing, elongations, shading, and ligatures. The second part deals with letter morphology, focusing on types of strokes shared by multiple letters: ascenders, descenders, horizontals, denticles, counters, and the shape of the nuqta (the dot made by the qalam, commonly used as a reference proportion in the canonical calligraphies, but not necessarily for the corpuses under scrutiny). A section also describes vowels and iḥmāl marks. This grouping gives an overview of the strokes that characterize the script.

This tool is not meant to provide an in-depth paleographical analysis but to help researchers identify the features that make a script unique and those that relate it to other scripts. It was designed from the outset to be reusable: by relying on shared, openly available concepts and properties, CallFront aims to offer an instrument that other researchers can adopt and adapt for their own corpora, encouraging comparison and interoperability across projects. This research is ongoing, and many of these scripts will benefit from further studies, allowing for further precisions in their description.

The CallFront vocabulary was adapted to fit a thesaurus structure using Openthéso, a Huma-Num platform in line with FAIR principles, ensuring long-term accessibility, interoperability, and reusability. CallFront's vocabulary is all available here, and can be downloaded and implemented by other databases and research projects.