Metadata for 3D objects

Metadata (the data about data) are data used to describe a digital object. Without metadata it would be very difficult to retrieve any digital object.

In case of the 3D-Icons project, there is more to it than meets the eye. And a bit more complex.  Andrea D'Andrea explains in this article how metadata and more specifically the way they are structured and organised are put into use to give access to the wide range of landscapes, buildings and objects captured by the partners in the project.

The 3D digitization workflow represented in the CARARE 2.0 Schema

The 3D digitization workflow represented in the CARARE 2.0 Schema

The scope of 3D-ICONS project is twofold: making available 3D contents for Europeana and developing a metadata schema able to capture all the semantic present in the digitisation process (provenance ) and in understanding and interpretation of data objects (paradata ). While as far as the data-acquisition of 3D cultural object is concerned, the existing technologies allow the former scope to be easily addressed, the latter, is innovative also for Europeana. 3D-ICONS identified the need to capture metadata relating to the digitization processes used and the provenance of 3D models to make it clear to end-users how and why a particular reconstruction was produced. One of the most important tasks of 3D-ICONS was therefore to update the previous CARARE schema [1]  by adding classes or entities and properties that would have made the original schema compliant with the 3D-ICONS requirements. Besides, as CARARE works like an intermediate schema between existing European standard and EDM, another step was to check the compatibility between CARARE and the latest advances in EDM.

In first year of the project provenance and paradata have been addressed and finally the metadata required have been specified as an extension to the CIDOC-CRM called CRMdig [2] . By considering the objectives of 3D-ICONS, we chose CRMdig because it allows a simple and clear description of the processes carried out to digitize and render a 3D model. Other initiatives, mainly DCMI’s Provenance Task Group [3] , use the provenance element to describe the metadata creation process.

While the provenance deals with “a record that describes entities and processes involved in producing and delivering or otherwise influencing that resource” [4] , paradata have been defined as information about human processes of understanding and interpretation of data objects. Examples of paradata include descriptions stored within a structured dataset of how evidence was used to interpret an artefact or a comment on methodological premises. It is closely related, but somewhat different in emphasis, to “contextual metadata”, which tend to communicate interpretations of an artefact or collection, rather than the process through which one or more artefacts were processed or interpreted.

Thanks to the recent developments of integration between CARARE and EDM and to the publication of object templates of EDM [5] , the updating of CARARE results in simplification. The last OWL version of EDM [6]  has been aligned to CIDOC-CRM Core Classes and some properties of CIDOC-CRM has reused in EDM allowing a more simple integration of CRMdig into EDM.

The deliverable D6.1, recently submitted [7] , describes the solutions adopted and the thesauri and authority files used by the partners and finally it contains some recommendations on the future possible scenarios in the LOD paradigm. The report focuses on the description of the starting point of the project in terms of definition of metadata for 3D objects. This introduces the CARARE and the EDM highlighting the state of art of the two schemas and showing some recent case-studies based on the integration of the two metadata schemas (CARARE-EDM). As far as provenance is concerned, the report introduces the CRMdig schema recently adopted and customized by the 3D-COFORM project. Finally, the report addresses the paradata principles  contained in the London Charter [8]  and how the input of paradata in the metadata schema could be relevant for the new strategy of Europeana.

The report outlines the new CARARE 2.0 schema (Fig. 1) based on the objectives of the 3D-ICONS and the results achieved in the mapping of CARARE on the EDM. It describes how provenance and paradata have been implementing through an event model approach correlating different events or activities that the object has taken part in (Figs. ).

[1] http://www.carare.eu/eng/content/download/4277/35150/file/CARARE%20metadata%20schema%20outline%20v1.1.pdf

[2]  M. Doerr, M. Theodoridou, CRMdig: A generic digital provenance model for scientific observation, Proceedings of TaPP  2011: 3rd USENIX Workshop on the Theory and Practice of Provenance , Heraklion, Greece (June 2011): http://static.usenix.org/events/tapp11/tech/final_files/Doerr.pdf

[3]  http://dublincore.org/groups/provenance/

[4]  http://www.w3.org/2005/Incubator/prov/wiki/What_Is_Provenance.

[5]  http://europeanalabs.eu/wiki/EDMObjectTemplatesProviders.

[6]  http://europeanalabs.eu/svn/europeana/trunk/corelib/corelib-solr-definitions/src/main/resources/eu/ rdf/EDM-v524-120820.owl.

[7]  http://3dicons-project.eu/eng/Media/Files/D6.1-Report-on-Metadata-Thesauri. The report has been prepared by CISA with the support of other partners (CETI, KMKG, MAP and MDR).

[8]  H. Denard, “A New Introduction to the London Charter” in A. Bentkowska-Kafel, D. Baker & H. Denard (eds.) Paradata and Transparency in Virtual Heritage  Digital Research in the Arts and Humanities Series (Ashgate, 2012) 57-71. http://www.londoncharter.org/fileadmin/templates/main/docs/ch6_denard.pdf.