GRDDL Gleaning Resource Descriptions from Dialects of Languages is used to denote that a web page contains RDF compatible data. GRDDL can be used to transform XML, XHTML, Microformats and other dialects through the use of transformation files like XSLT or transformation documents published for widely used name spaces Microformats or the health care industry's HL7.

Using GRDDL to harvest RDF data from existing pages on the web, allows millions of existing data elements to be parsed, extracted and reformatted without the need for site owners to republish their data using new, industry standard vocabularies. The data can the be linked to other open data around the web.

There are a number of tools being developed or enhanced to incorporate the GRDDL recommendation. A reader is being developed for the Jena Semantic Web Framework. Tools, like TopBraid Composer, that build on the Jena Framework will glean the benefits through that reader.