I use this:
<!DOCTYPE html>
<html vocab="http://www.w3.org/2011/rdfa-context/rdfa-1.1">
<!-- you can use one or more prefixes
cat: http:
qb: http:
grddl: http:
ma: http:
owl: http:
rdf: http:
rdfa: http:
rdfs: http:
rif: http:
rr: http:
skos: http:
skosxl: http:
wdr: http:
void: http:
wdrs: http:
xhv: http:
xml: http:
xsd: http:
prov: http:
sd: http:
org: http:
gldp: http:
cnt: http:
dcat: http:
earl: http:
ht: http:
ptr: http:
cc: http:
ctag: http:
dc: http:
dc11: http:
dcterms: http:
foaf: http:
gr: http:
ical: http:
og: http:
rev: http:
sioc: http:
v: http:
vcard: http:
schema: http:
describedby:http:
license: http:
role: http:
-->
<head>
<meta property="og:title dc:title" content="This is a test!">
<meta property="dc:description" content="This is a description test">
</head>
<body>
<header typeof="role:banner schema:Organization">
<div>
<h1>
<a href="/" title="home" rel="home" accesskey="1">
<img class="logo" property="schema:image" src="my-image.png" width="160" alt="My logo">
</a>
</h1>
<h2>
<span property="schema:description">creative design and rock-solid development</span>
</h2>
</div>
</header>
...and so on...
</body>
</html>
You can read more about this here http://rdfa.info