I've confirmed that SPARQL 1.1 update syntax is not yet in place for Sesame 2.4. Therefore we will proceed with a simple REST API for POSTing RDF statements to be inserted into (or removed from) the database.
Interesting extensions which we have implemented for various applications include the ability to CONSTRUCT the statements to be inserted or removed based on a query. This can be readily implemented as extensions of a basic REST API.
The API will require either triples or quads, depending on the mode of the backing KB instance. The MIME type of the POST payload will be used to parse the payload. It will be an error to send triples to a quad store or quads to a triple store.