Citations with added RDFa

The page Citation_in_digital_scholarship describes a convention for making citations that relies on the 'class' and 'title' attributes when implemented in (x)html. This page further elaborates that convention by describing how to add RDFa to conformant citations.

Sample sentences:
 * Ephesus demonstrates the potential complexity of ancient Mediterranean urban centers.
 * The first chapter of Herodotus is an early example of Greek historical writing.
 * Herodotus (1.78) gives a brief characterization of the city of Babylon
 * Millar (2001) stresses the polyglot nature of the Roman near east.

With citation markup added:
 * Ephesus ...
 * The first chapter of Herodotus...
 * Herodotus (1.78) gives a brief ...
 * Millar (2001) ...

Discussion
The 'Citation with added RDFa' convention allows three basic types of information to be added to a citation:
 * The nature of the entity being cited (@typeof). Dublin Core is the default typology. Authors can add their own typology as needed.
 * The reason the entity is being cited (@rel).
 * The relationship of the web-based resource being cited to the underlying concept being invoked (@rel).

The representation of these three types of information can be explored by way of example using the sample sentences defined above.
 * Herodotus (1.78) gives a brief ...
 * Ephesus ...

In the second RDFa example, the use of 'skos:definition' makes clear that the resource at 'http://pleiades.stoa.org/places/599612' is not Ephesus itself, but a definition thereof.

RDFa Pattern 1
Focusing just on the 'a' element, the following RDFa provides additional levels of detail: Herodotus (1.78)

Assuming this snippet is found with a document with the URI http://example.org/article01 that contains the necessary prefix declaration, it produces the following RDF in Turtle format:  []   a dc:Text ; dc:references .

RDFa Pattern 2
If it is clear that an internet-based resource (aka a "web page") provides a description or definition of a cited entity, use: Ephesus</a> This produces: <http://example.org/article01> []   a dc:Location ; dc:references <http://pleiades.stoa.org/places/599612>; skos:definition <http://pleiades.stoa.org/places/599612>.

RDFa Pattern 3
Adding some hierarchy allows for more expressive RDFa &lt;span class="citation" rel="dc:references"> Ephesus</a>

Which produces the following RDF/Turtle: @prefix dc: <http://purl.org/dc/terms/>. @prefix skos: <http://www.w3.org/2004/02/skos/core#>. <http://example.org/article01> dc:references [ a dc:Location ; skos:definition <http://pleiades.stoa.org/places/599612> ] ;

The RDF can be read as saying, "There is a document at http://example.org/article01 that references a location that is defined at http://pleiades.stoa.org/places/599612 ." This is the preferred markup of conformant citations that rely on RDFa to add further information.