Ontology seeks to describe categories and relationships of existence, to define entities and types of entities within a given domain. At its simplest, an ontology is a set of entities and relations. The aim is to embed assumptions, definitions, and procedures for use and integration, in explicit ontologies that can make that knowledge reusable. It is this systematic representation of the relationships among concepts, and of procedural knowledge, which makes it a potentially useful approach to underpinning our interpretation of the aerial images.
'The scientific utility of digital data is absolutely contingent on the availability of adequate metadata that document the data sets. Metadata include (1) syntactic information, having to do with how databases are formatted, how observations are scaled, and how the data fields are related, and (2) semantic information that documents the measured quantities; units; sampling procedures; temporal, spatial, and cultural contexts; recording procedures; and classification systems' (Kintigh 2006, 573).
The need for metadata has become well established, not least through the efforts of the Archaeology Data Service (ADS) (e.g. Bewley et al. 1998; Richards and Robinson 2000), but the development of ontologies has been slower.
So how do we approach this? The main implementations have been based upon developing a Resource Description Framework (RDF), and a Web Ontology Language (OWL), that facilitates formal descriptions of concepts, terms, and relationships within a given domain.
'An OWL ontology may include descriptions of classes, properties and their instances. Given such an ontology, the OWL formal semantics specifies how to derive its logical consequences, i.e. facts not literally present in the ontology, but entailed by the semantics. These entailments may be based on a single document or multiple distributed documents that have been combined using defined OWL mechanisms' (W3C 2004).
There are a number of packages available to assist in the OWL creation (see Denny 2004), many of which are open source. There is much work to be done to develop this process, although work has started in a number of archaeological fields (for example, see Cripps et al. 2004).
For this project we have started to develop a working model for the aerial photographic and satellite data. We are using Protégé, a free and platform-independent open source ontology editor and knowledge-based framework, used for developing and managing large terminologies, ontologies, and knowledge bases. It has good support for different exchange languages (e.g. RDF, OWL, XML).
The first step has been to define the assumptions and entities that are involved, and their inter-relationships. To encourage debate about this material a weblog has been created to host (time-limited) debates, which can themselves be subsequently archived within the ADS, not lost at the end of the project or website.
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Last updated: Mon Sept 29 2008