While trying some HTML from Drupal in Play, I found it sometimes doesn't return the expected triples. I've isolated the bug to be coming from a script element in <head>. To reproduce, try the following snippet in Play and note that no triples are generated for the RDFa inside body (while pyRDFa and Gregg's distiller do generated the expected triples).
<span vocab="http://schema.org/" typeof="Document">
<a property="url" href="http://www.w3.org/TR/rdfa-primer/">
<span property="title">RDFa 1.1 Primer</span></a>.
Here are the triples I get when I run Green Turtle "manually":
<> http://www.w3.org/ns/rdfa#usesVocabulary http://schema.org/
<:1> http://www.w3.org/1999/02/22-rdf-syntax-ns#type http://schema.org/Document
<:1> http://schema.org/url http://www.w3.org/TR/rdfa-primer/
<_:1> http://schema.org/title "RDFa 1.1 Primer"
Grrr... OK. Those links had angle brackets around them but github interpreted them as links.
fixed and deployed http://rdfa.info/play/