RDFa Support

RDFa Support

RDFa is now a part of Drupal 7 core. RDFa is a format for structuring data, and makes it easy to share information between various kinds of sites. In order to make full use of Drupal 7 and RDFa, you must also install the RDF extensions module.

Here are a few introductions to the topic of RDFa and Drupal 7:

RDFa Namespaces

The table that follows outlines the various namespace vocabulary libraries available to Drupal. Required is the installation of ARC2, a PHP library that contains the various namespaces and vocabularies for working with RDFa in Drupal 7. It also provides a MySQL-based triplestore.

content http://purl.org/rss/1.0/modules/content//td>
dc http://purl.org/dc/terms/
foaf http://xmlns.com/foaf/0.1/
og http://ogp.me/ns#
rdfs http://www.w3.org/2000/01/rdf-schema#
sioc http://rdfs.org/sioc/ns#
sioct http://rdfs.org/sioc/types#
skos http://www.w3.org/2004/02/skos/core#
xsd http://www.w3.org/2001/XMLSchema#
owl http://www.w3.org/2002/07/owl#
rdf http://www.w3.org/1999/02/22-rdf-syntax-ns#
rss http://purl.org/rss/1.0/
site http://www.digitallibrarycentral.com/ns#
schema http://schema.org/

RDFa attributes for the Leslie Jones Collection

The second table (below) outlines the current mappings for the data elements in the Leslie Jones Collection. Currently, the primary vocabularies used to map the entities with vocabulary attributes are two: 1) Dublic Core, and 2) Schema.org. Unqualified Dublin Core was used to describe this collection primarily because it is the most common and most general data description format, developed and endorsed both by library science and web (W3C) professionals. It also allows a simple way to schematically map our fields to the most common harvesting protocol, OAI-PMH (see the next section for how our set of Dublin Core attributed fields have been harvested using this protocol).

Additionally, schema.org is the most recent element set that most search engines (e.g., Google, Bing) use to provide rich snippets in the retrieved summary of results after a web search.

Over time, other vocabularies attributes will be assigned to the metadata elements. What you see below is dated June 2013.

Creator schema:creator, dc:creator property
Image schema:image, dc:identifier rel
Title-Description schema:summary, dc:title, dc:description property
BPL Accession dc:identifier property
Subject Series schema:about, dc:subject rel
TGM Headings schema:keywords, dc:subject rel
Name Headings schema:about, dc:subject rel
Publisher schema:provider, dc:publisher property
Type schema:associatedMedia, dc:type property
Medium schema:associatedMedia, dc:format property
Extent schema:height, schema:width, dc:format property
Genre schema:genre, dc:format property
Rights schema:copyrightHolder, dc:rights property
Rights schema:copyrightHolder, dc:rights property
Preferred Credit schema:accountablePerson property
Collection schema:isPartOf property

Please note that after installing the RDF extension module, Drupal 7 incorporates many other vocabulary attributes to various parts of each page (e.g., comments, comment_count, upload date, modification/change tracking, url etc.). These are not outlined above, but can be discovered by viewing the page source.

It is also worth mentioning that each image within the Leslie Jones Collection is fully RESTful (i.e., allows for Representationl State Tranfer), and thus permits the future implementation of various standardised web service formats to extract the collection in whole or in part. To see the RDFa markup in action for one of the Leslie Jones photographs in this collection, visit any one image (e.g., the first image in the collection), and along with the other metadata you will see link entitled "RESTful XML/RDF."