"In controlled environments, e.g. on a single site, or in a single person's
media library, or within a small coherent community where all the
participants have compatible goals, it is possible to get enough
discipline that metadata is both reliable and useful. And for such
communities we have a raft of extension mechanisms, and clashes can be
avoided easily by simply using names that nobody in the community is
already using.

"But as soon as this kind of thing is applied to people outside the
tightnit community, the metadata becomes an utter mess, misused, wrong,
missing, syntactically incorrect, semantically incorrect, unusable. We
have shown time and time again that when metadata mechanisms face the
wider Web community, they fail. Ignoring this doesn't make it go away."

This version accompanies the developement of RDFa 1.1 Core. As that document is not final yet, this service, and the underlying code, will change frequently until the development of RDFa 1.1 is finalized. The implementation may actually run ahead of the “official” version and implement the version in the editors’ draft already… Also, the package available for download may be out of sync with the code running this service.

This is a suggestion to consider @resource as preferable over @about. The purpose is to promote a slightly simpler and more uniform practice of RDFa use, especially in the RDFa Lite subset.

In order to consolidate and decode some of the information you need to sift through when learning about rich snippets, we've created this visual guide to walk through the basics, fundamental types, implementation, and benefits of utilizing them.   

Microformats, RDFa and microdata all enable consumers to extract data from HTML pages. This data may be embedded within enhanced search engine results, exposed to users through browser extensions, aggregated across websites or used by scripts running within those HTML pages.

This guide aims to help publishers and consumers of HTML data use it well. With several syntaxes and vocabularies to choose from, it provides guidance about how to decide which meets the publisher's or consumer's needs. It discusses when it is necessary to mix syntaxes and vocabularies and how to publish and consume data that uses multiple formats. It describes how to create vocabularies that can be used in multiple syntaxes and general best practices about the publication and consumption of HTML data.

This should give a rough overview over the usage of the different formats.

Like the DTD-based W3C markup validation service, this service checks the markup validity of Web documents, but instead uses the backend from the Validator.nu engine. The default setting of the validator validates HTML5 with RDFa 1.1. Lite and with microdata, the two simpler syntaxes to add structured data to HTML.

Web Data Commons will extract all Microformat, Microdata and RDFa data that is contained in the Common Crawl corpus and will provide the extracted data for free download in the form of RDF-quads as well as CSV-tables for common entity types (e.g. product, organization, location, ...).

The purpose of this cookbook is to document and discuss the use of RDF in digital humanities. Its focus is specific applications as found in the real world, though a few general principles are suggested. It assumes that you’re vaguely comfortable with RDF and RDFa.

This post attempts to clarify those technical issues by providing an easy-to-read list of similarities and differences between RDFa, Microdata and Microformats. A simple table summarizing all features across each structured data syntax is listed below. Each feature is linked to a brief explanation of the feature toward the bottom of the page.

More and more of the world's data is moving onto the Web. We want to share, re-mix and use this data to build more awesome Web applications. Using structured data technologies to mark up people, places, events, recipes, ratings, music, movies and products on the Web makes everybody's life easier. This site will help you learn about big data, the semantic web, and the practical application of technologies such as Microformats, RDFa, Microdata and JSON-LD.

Nick Carr accuses Google of using #RDFa and #linkeddata to conspire against Grandma: #ldow2011

It must be simple for Web developers to extract and utilize structured information from a Web document. This document details such a mechanism; an RDFa Document Object Model Application Programming Interface (RDFa DOM API) that allows simple extraction and usage of structured information from a Web document.

rdfQuery is an easy-to-use Javascript library for RDF-related processing. You can use it to parse RDFa embedded within your page, query over the facts it contains, and reason to produce more facts. In concert with an server-side triplestore, rdfQuery can be used to create interfaces for editing the semantic web.

Create semantically enhanced content, without knowing about semantic technologies, with automatically proposed annotations.

What Google does with embedded metadata.

We need to partition the idea of extensibility into two parts: extending the platform vs. extending the language.

It would seem important that the Web easily enable small-time users of data to efficiently communicate with one another, without the need to have one of the giants as an intermediary.

CSS is an external file that specifies how your document should look; RDF-EASE is an external file that specifies what your document means.

Whilst there are many ways to publish metadata, we're going to focus on the use of RDFa, and how to either embed the information in web-pages, or provide a separate XML feed.

The Ubiquity RDFa project provides a JavaScript RDFa parser that can be used either on its own, or with other parts of the Ubiquity library.