| dc:abstract
| Abstract
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 Core is a specification for attributes to express structured data
in any markup language. The embedded data already available in the
markup language (e.g., HTML) can often be 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 [RDF11-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 of the same goals 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 vocabulary
being used.
This document is a detailed syntax specification for RDFa, aimed at:
- those looking to create an RDFa Processor, and who therefore need a
detailed description of the parsing rules;
- those looking to integrate RDFa into a new markup language;
- those looking to recommend the use of RDFa within their
organization, 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 Processor 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 Document
First, 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 [RDFA-PRIMER] to be a better introduction.
If you are already familiar with RDFa, and you want to examine the
processing rules — perhaps to create an RDFa Processor — 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 markup 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. This document only contains
enough background on RDF to make the goals of RDFa more clear.
Note RDFa is a way of expressing RDF-style
relationships using simple attributes in existing markup languages
such as HTML. RDF is fully internationalized, and permits the use of
Internationalized Resource Identifiers, or IRIs. You will see the term
'IRI' used throughout this specification. Even if you are not familiar
with the term IRI, you probably have seen the term 'URI' or 'URL'.
IRIs are an extension of URIs that permits the use of characters
outside those of plain ASCII. RDF allows the use of these characters,
and so does RDFa. This specification has been careful to use the
correct term, IRI, to make it clear that this is the case. Note Even though this specification exclusively
references IRIs, it is possible that a Host Language will
restrict the syntax for its attributes to a subset of IRIs
(e.g., @href in HTML5). Regardless of
validation constraints in Host Languages, an RDFa Processor
is capable of processing IRIs. Abstract
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 Core is a specification for attributes to express structured data
in any markup language. The embedded data already available in the
markup language (e.g., HTML) can often be 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 [RDF11-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 of the same goals 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 vocabulary
being used.
This document is a detailed syntax specification for RDFa, aimed at:
- those looking to create an RDFa Processor, and who therefore need a
detailed description of the parsing rules;
- those looking to integrate RDFa into a new markup language;
- those looking to recommend the use of RDFa within their
organization, 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 Processor 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 Document
First, 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 [RDFA-PRIMER] to be a better introduction.
If you are already familiar with RDFa, and you want to examine the
processing rules — perhaps to create an RDFa Processor — 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 markup 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. This document only contains
enough background on RDF to make the goals of RDFa more clear.
Note RDFa is a way of expressing RDF-style
relationships using simple attributes in existing markup languages
such as HTML. RDF is fully internationalized, and permits the use of
Internationalized Resource Identifiers, or IRIs. You will see the term
'IRI' used throughout this specification. Even if you are not familiar
with the term IRI, you probably have seen the term 'URI' or 'URL'.
IRIs are an extension of URIs that permits the use of characters
outside those of plain ASCII. RDF allows the use of these characters,
and so does RDFa. This specification has been careful to use the
correct term, IRI, to make it clear that this is the case. Note Even though this specification exclusively
references IRIs, it is possible that a Host Language will
restrict the syntax for its attributes to a subset of IRIs
(e.g., @href in HTML5). Regardless of
validation constraints in Host Languages, an RDFa Processor
is capable of processing IRIs. |
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