GRDDL is a markup format for Gleaning Resource Descriptions from Dialects of Languages. It is a W3C Recommendation
W3C recommendation
A W3C Recommendation is the final stage of a ratification process of the World Wide Web Consortium working group concerning a technical standard. This designation signifies that a document has been subjected to a public and W3C-member organization's review. It aims to standardise the Web technology...
Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....
XHTML is a family of XML markup languages that mirror or extend versions of the widely-used Hypertext Markup Language , the language in which web pages are written....
. The GRDDL specification shows examples using XSLT
XSLT
XSLT is a declarative, XML-based language used for the transformation of XML documents. The original document is not changed; rather, a new document is created based on the content of an existing one. The new document may be serialized by the processor in standard XML syntax or in another format,...
, however it was intended to be abstract enough to allow for other implementations as well. It became a Recommendation on September 11, 2007.
XHTML and transformations
A document specifies associated transformations, using one of a number of ways.
For instance, an XHTML document may contain the following markup:
Document consumers are informed that there are GRDDL transformations available in this page, by including the following in the profile attribute of the head element:
http://www.w3.org/2003/g/data-view
The available transformations are revealed through one or more link elements:
XHTML is a family of XML markup languages that mirror or extend versions of the widely-used Hypertext Markup Language , the language in which web pages are written....
1.x only. The profile attribute has been dropped in HTML5, including its XML serialisation.
A microformat is a web-based approach to semantic markup which seeks to re-use existing HTML/XHTML tags to convey metadata and other attributes in web pages and other contexts that support HTML, such as RSS...
s, there is usually a specific profile.
For instance, a document with hcard information should have:
The GRDDL aware agent can then use that profileTransformation to extract all hcard data from pages that reference that link.
XML and transformations
In a similar fashion to XHTML, GRDDL transformations can be attached to XML documents.
XML namespace transformations
Just like a profileTransformation, an XML namespace can have a transformation associated with it.
This allows entire XML dialects (for instance, KML or Atom) to provide meaningful RDF.
An XML document simply points to a namespace
and when fetched, http://example.com/1.0/ points to a namespaceTransformation.
This also allows very large amounts of the existing XML data in the wild to become RDF/XML with a very minimal effort from the namespace author.
Output
Once a document has been transformed, there is an RDF
Resource Description Framework
The Resource Description Framework is a family of World Wide Web Consortium specifications originally designed as a metadata data model...
representation of that data.
This output is generally put into a database and queried via SPARQL
SPARQL
SPARQL is an RDF query language; its name is an acronym that stands for SPARQL Protocol and RDF Query Language. It was made a standard by the RDF Data Access Working Group of the World Wide Web Consortium, and considered as one of the key technologies of semantic web...
.
GRDDL consumers (also known as GRDDL aware agents)
Virtuoso Universal Server is a middleware and database engine hybrid that combines the functionality of a traditional RDBMS, ORDBMS, virtual database, RDF, XML, free-text, web application server and file server functionality in a single system...
PHP is a general-purpose server-side scripting language originally designed for web development to produce dynamic web pages. For this purpose, PHP code is embedded into the HTML source document and interpreted by a web server with a PHP processor module, which generates the web page document...
A microformat is a web-based approach to semantic markup which seeks to re-use existing HTML/XHTML tags to convey metadata and other attributes in web pages and other contexts that support HTML, such as RSS...
, a simplified approach to semantically annotate data in websites
Embedded RDF is a syntax for writing HTML in such a way that the information in the HTML document can be extracted into Resource Description Framework...
