You are currently viewing a snapshot of taken on April 21, 2008. Most of this content is highly out of date (some pages haven't been updated since the project began in 1998) and exists for historical purposes only. If there are any pages on this archive site that you think should be added back to, please file a bug.

Dublin Core Metadata Initiative

Mozilla RDF: Metadata Vocabularies


RDF gives the Web an infrastructure to support a diverse metadata environment. The RDF model makes it easy for multiple metadata vocabularies to co-exist within the same general framework. In Mozilla, a number of different applications (sitemaps, bookmarks, mail/news, smart browsing etc) use RDF as an interoperability layer, sharing (for example) storage, query and visualisation components. Each of these applications make use of descriptive vocabularies. By utilizing common vocabularies it is possible to increase the potential for interoperability among RDF applications.

Current Status

This page serves as a registry of metadata vocabularies used in the Mozilla environment. Currently this page describes expected future best-practice rather than existing implementation. Work to date on Mozilla has used a temporary, ad-hoc vocabulary identified by the URI '' and the informal namespace prefix 'NC'. There is an open bug [Bug 12161] [HELPWANTED] clean up vocabulary usage against Mozilla's current 'NC' vocabulary.

"Currently, our "NC" vocabulary is a pile of ad-hoc hacks that have evolved over time. We need to go on a crusade to formalize this and publish it." [BUG 12161]

This page is intended to track documentation and debate concerning appropriate metadata vocabularies for Mozilla, and to serve as a point of connection (and 'help wanted' notice!) for the wider metadata community.

Mozilla, RDF and the Dublin Core

The Mozilla RDF implementation provides an open, standards-based information management environment. Just as it makes sense to minimise redundancy between Mozilla-specific applications (eg. sitemaps and bookmarks), it is also important to minimise redundancy between Mozilla and other RDF-based applications.

Tremendous benefit can be gained across applications that agree to utilize common vocabularies. The Dublin Core Metadata Initiative (DCMI) is an open, international community-driven standards organization that facilitates the development of RDF-based descriptive vocabularies. The Dublin Core Element Set, a simple 15-element base vocabulary targeted at resource discovery, Web directory and search engine applications, has been widely adopted by content creators and 3rd party metadata services (eg. Netscape's Open Directory project). The consensus-building role played by the Dublin Core within the metadata community is similar to that played by the Mozilla Organization and related initiatives in the 'open source' software world. It should be possible to leverage the work of the DC community to provide non-proprietary, multilingual vocabularies for Mozilla-based applications.

Mozilla Applications

Here we list a number of RDF applications with Mozilla, and sketch migration paths from the 'NC' vocabulary where this seems feasible...

In many cases, the Dublin Core Element Set appears to provide facilities adequate to support a significant proportion of functionality (ie. 'title', 'description', 'subject' etc can replace similar concepts invented in the NC namespace). Where DC semantics do not entirely address the needs of Mozilla applications, it should be possible to layer on top of the DC semantics through combining DC properties with other application specific constructs. In this way, other RDF/DC services will have at least some partial understanding of RDF data created using this approach.

(Preliminary proposals; to be completed and illustrated...)
  • Mail/news
  • (to be reviewed)
  • sitemaps
  • (proposal: Dublin Core)
  • bookmarks
  • (proposal: Dublin Core)
  • smartbrowsing
  • (proposal: Dublin Core)
  • search results
  • (proposal: Dublin Core)
  • flash notations
  • (to be reviewed)


RDF and XML provide some facilities to support the development of multilingual, internationalized metadata vocabularies. The Dublin Core Working Group on Multiple Languages has been working on practical approaches to deploying RDF metadata in a multilingual environment.

The mission of the Working Group on Dublin Core in Multiple Languages is to coordinate the development of the Dublin Core as a multilingual metadata standard. As of June 1998, our focus is on creating a distributed registry of Dublin Core in multiple languages using the Resource Description Framework (RDF), an emerging standard syntax for expressing metadata schemas on the Web. [DC International Charter]

Further information about DC in Multiple Languages can be obtained from the Working Group home page, including details of the mailing list, membership of the group, meeting reports and working drafts showing the use of distributed, language-tagged RDF Schema annotations for multilingual DC/RDF metadata.

Next steps...

This document is a work in progress. We need to look in more detail at the subtleties of migrating to DC vocabulary, at the effort involved in bulk-fixing the Mozilla filetree and at issues such as the reflection of language-tagged labels into the Mozilla RDF APIs. We also need confirmation of the case of the DC 1.0 and 1.1 vocabularies ('creator' or 'Creator'). See also the thread on mozilla-rdf 'RDF vocabulary for mail/news' and the list of mail/news vocabulary items currently in use. We should also look at using the RDF Schema 'subPropertyOf' relation to express mappings from things like NC:Sender to properties with broader semantics such as DC:Creator... (and wrapping a subProperty-aware javascript function around the Mozilla RDF store so we might ask a question about DC:Creator and have data returned that was natively using NC:Sender?)

Last Updated: $Id: vocabs.html,v 1.5 1999/09/17 08:29:07 Exp $