Facebook Open Graph crawlers use RDF in HTML head-meta elements conveying data about authors of web pages. Similarly, Google Corporate Contacts extracts RDF fr

Facebook Open Graph crawlers use RDF in HTML head-meta elements conveying data about authors of web pages. Similarly, Google Corporate Contacts extracts RDF from web pages (but can also use JSON microdata). W3C's newly published open social standard is based on RDF (as JSON-LD) I believe. RDF and SPARQL has lots of uses in libraries and bibliographic apps such as citation managers, as well as in publication of open data, in particular medical and bio informatics data. Dublin Core (as RDF) is frequently used for standard document metadata, for example in PDF.