The current Web is primarily made up of an enormous number of
documents that have been created using HTML. These documents
contain significant amounts of structured data, which is largely
unavailable to tools and applications. When publishers can express
this data more completely, and when tools can read it, a new world
of user functionality becomes available, letting users transfer
structured data between applications and web sites, and allowing
browsing applications to improve the user experience: an event on a
web page can be directly imported into a user's desktop calendar; a
license on a document can be detected so that users can be informed
of their rights automatically; a photo's creator, camera setting
information, resolution, location and topic can be published as
easily as the original photo itself, enabling structured search and
sharing.RDFa is a specification for attributes to express structured
data in any markup language. This document specifies how to use
RDFa with XHTML. The rendered, hypertext data of XHTML is reused by
the RDFa markup, so that publishers don't need to repeat
significant data in the document content. The underlying abstract
representation is RDF [RDF-PRIMER], which lets publishers build
their own vocabulary, extend others, and evolve their vocabulary
with maximal interoperability over time. The expressed structure is
closely tied to the data, so that rendered data can be copied and
pasted along with its relevant structure.The rules for interpreting the data are generic, so that there
is no need for different rules for different formats; this allows
authors and publishers of data to define their own formats without
having to update software, register formats via a central
authority, or worry that two formats may interfere with each
other.RDFa shares some use cases with microformats [MICROFORMATS]. Whereas microformats
specify both a syntax for embedding structured data into HTML
documents and a vocabulary of specific terms for each microformat,
RDFa specifies only a syntax and relies on independent
specification of terms (often called vocabularies or taxonomies) by
others. RDFa allows terms from multiple independently-developed
vocabularies to be freely intermixed and is designed such that the
language can be parsed without knowledge of the specific term
vocabulary being used.This document is a detailed syntax specification for RDFa, aimed
at:those looking to create an RDFa parser, and who therefore need
a detailed description of the parsing rules;those looking to recommend the use of RDFa within their
organisation, and who would like to create some guidelines for
their users;anyone familiar with RDF, and who wants to understand more
about what is happening 'under the hood', when an RDFa parser
runs.For those looking for an introduction to the use of RDFa and
some real-world examples, please consult the RDFa Primer.How to Read this DocumentIf you are already familiar with RDFa, and you want to examine
the processing rules — perhaps to create a parser —
then you'll find the Processing Model
section of most interest. It contains an overview of each of the
processing steps, followed by more detailed sections, one for each
rule.If you are not familiar with RDFa, but you are familiar
with RDF, then you might find reading the Syntax Overview useful, before looking at
the Processing Model since it gives a range
of examples of XHTML mark-up that use RDFa. Seeing some examples
first should make reading the processing rules easier.If you are not familiar with RDF, then you might want to take a
look at the section on RDF
Terminology before trying to do too much with RDFa. Although
RDFa is designed to be easy to author—and authors don't need
to understand RDF to use it—anyone writing applications that
consume RDFa will need to understand RDF. There is a lot
of material about RDF on the web, and a growing range of tools that
support RDFa, so all we try to do in this document is provide
enough background on RDF to make the goals of RDFa clearer.And finally, if you are not familiar with either RDFa
or RDF, and simply want to add RDFa to your documents,
then you may find the RDFa Primer [RDFaPRIMER] to be a better introduction.
Owner
Standardisation body