In the following snippet of RDFa:
<span about="example.com/subjectURI" rel="example.com/predicateURI" property="literalText"></span>
the URI in the about= attribute is the subject (OK the entity referred to by the URI, but you get the idea), rel indicates the predicate and property indicates a literal object. I know that using the rev attribute for the predicate reverses the subject and the object so that about= now refers to the object of the RDF statement. However, from what I have read, it doesn't seem that literals are allowed to be subjects. So, would the following be legal?
<span about="example.com/objectURI" rev="example.com/predicateURI" property="literal-text-as-a-subject"></span>
Now one could argue that literal text could be a subject of a statement. For instance Steven Colbert may write the following line of RDFa:
<span about="www.stevencolbert.com/verytruthy" rev="www.stevencolbert.com/truthyness" property="Only geeks would care about whether one could use @rev with @property, whatever the hell that means."></span>