Figure 4: Pilot System showing query results with hyperlinks to Silchester database
Two major prototypes were developed in the course of the project; an initial Pilot client application followed by a web Demonstrator. Both operated over a triple store using a web service architecture to access the concept and data RDF information. Different approaches to the implementation and the user interface were followed in the two systems.
The Pilot offered access to a wider range of the data fields mapped to the ontology than exposed in the Demonstrator. These included references to photographs, along with spatial and temporal coordinates of contexts and finds. Accurate plotting and visualisation of locations would be a requirement in future operational systems, involving many datasets from the same geo-spatial region, However, it was not a STAR project aim and was not carried forward to the Demonstrator, owing to project resource limitations (discussed further in section 4.1).
The Pilot verified that the data mapping/extraction techniques and RDF representation would support interoperability via the CRM and that the SPARQL language could achieve browsing and search results. It was used to gather feedback and provide scenarios for a series of project workshops with representative archaeological users, which informed further development. Figure 4 shows the Pilot user interface, which employed colour coding to indicate the data source (MOLA and OASIS were not part of the Pilot). We see that after an initial string search the full CRM-EH ontology is exposed in the user interface; it is possible to browse the ontology, with search results offering entry points to the structured data. This allows a user to browse related data items, by following chains of relationships within the CRM-EH. In the screendump, a note from a ContextFind has an associated RecordPhotograph, which is linked via a URI identifier to a digital photograph on the Silchester Project (Clarke et al. 2007) online database at Reading University. Figure 4 also demonstrates the use of the STAR (SKOS) terminology web service for query expansion in the initial string search (brooch is expanded with related concepts suggested from the EH thesauri).
From feedback at the workshops and project meetings, browsing the full chain of connections between elements of the ontology proved cumbersome, particularly given the event-based nature of the CRM. Exposing the full ontology resulted in too verbose a user interface and was overly complicated for most archaeological users. Accordingly, a different approach, hiding the complexity of the underlying ontology, was followed in the subsequent Demonstrator. The Pilot's dynamic linking to other online databases and the SKOS-based query expansion were not further pursued, due to time constraints, but were considered promising features that will be considered in future work.
The Demonstrator is a web application, aiming to be browser agnostic (it has been tested with recent versions of Chrome, Internet Explorer, Firefox, Opera and Safari browsers). In addition to offering string search of Note fields, it focuses upon the possibilities of semantic search based on controlled (URI) identifiers and makes more use of SPARQL than the Pilot. Users can dynamically build queries (by selecting the relevant tab) to search for Samples, Finds, Contexts or interpretative Groups (of contexts). The default is to search across all datasets but it is possible to restrict a search to a specific dataset (via site). As the user selects interface controls, an underlying semantic query is automatically constructed in terms of the corresponding ontological entities. This extends to connections between elements, for example Finds of a particular type within Contexts of a particular type, or contexts having a stratigraphic relationship with another context. Thus typical queries might be Context of Type hearth containing Find of Type coin (illustrated in Fig. 5) or Contexts of Type Furnace Stratigraphically above Contexts of Type floor. Results can include items from different datasets and from OASIS grey literature reports. The next section explores some illustrative scenarios in more detail.
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