Let's return to our simple example from an earlier section:
<head>
<meta name="author" content="Mark Birbeck" />
<meta name="geo.position" content="43.95;4.833333" />
</head>
Recall that we said that with 'implicit knowledge' we could interpret this as the following set of triples:
<http://internet-apps.blogspot.com> dc:creator
[
foaf:name "Mark Birbeck";
geo:lat "43.95";
geo:long "4.833333"
] .
(Remember that I mapped the properties to existing vocabularies that seemed appropriate.)
Our next step is to look at how we can mark this up unambiguously; i.e., in such a way that we can dispense with the 'implicit' knowledge.
The RDFa mark-up for this actually mirrors the N3 quite closely (assuming that this is in a document stored at http://internet-apps.blogspot.com):
<head>
<link rel="dc:creator" href="#about" />
<meta about="#author" property="foaf:name" content="Mark Birbeck" />
<meta about="#author" property="geo:lat" content="43.95" />
<meta about="#author" property="geo:long" content="4.833333" />
</head>
This is a generic solution because statements in the head section that follow the layout of the first statement, i.e.:
<meta property="p" content="o" />
are always statements about the document itself, whilst statements with an about attribute, i.e., this pattern:
<meta about="s" property="p" content="o" />
always relate to the item designated by the URI in the about attribute.
Our mark-up has two sets of statements; the first concerns the document itself and is a reference to the 'thing' that created it:
<link rel="dc:creator" href="#about" />
The second lot of statements describe this 'thing' that created the document, and tell us its name and where it is:
<meta about="#author" property="foaf:name" content="Mark Birbeck" /> <meta about="#author" property="geo:lat" content="43.95" /> <meta about="#author" property="geo:long" content="4.833333" />
This separation of the two lots of statements means that even when we don't know anything about what the data 'means' we can still tell which of our resource pairs its about; we can tell if it's about the web-page or the web-page's author, the web-page or the conference, the web-page or the conference session, the web-page or the car, the web-page or the planet, the web-page or the Zanussi washing-machine, and so on.