X3D Fragment Identifiers — Extending the Open Annotation Model to Support Semantic Annotation of 3D Cultural Heritage Objects over the Web

Abstract

This paper describes extensions made to the Open Annotation (OA) data model to enable the semantic annotation of points, surface regions and volumetric segments on 3D cultural heritage artefacts. More specifically it describes how the X3D (Extensible 3D Graphics) standard has been adapted to support concise, machine-processable and persistent 3D fragment identifiers. Methods to improve the efficiency of capturing, compressing and processing the X3D fragment identifiers are also described. The proposed X3D extensions are implemented and evaluated using a test-bed of 3D representations of ancient Greek Vases. The advanced annotation and search services that are achievable as a result of combining OA and X3D for the underlying annotation data model are also described. The benefits of this approach are demonstrated by measuring the improvements in file size and response times that are achieved. We also present evaluation results that indicate that the X3D approach combined with innovative run-length encoding (RLE) and innovative processing methods, improves the speed and efficiency of searching, retrieving and rendering annotations on 3D digital objects, over the Web.