CellML

The CellML API currently only provides access to the RDF in a model by trying to find the
rdf:Description element corresponding to the cmeta:id of an element. However, this is extremely
inadequate, because triples in the graph that we want to access could be stored anywhere in the
corresponding model, especially after we have followed a few arcs.
The API would clearly need to work well together with the existing system where changes to the XML
immediately take effect (rather than having a distinct RDF/XML parse phase), although this could be
implemented internally using the version serial number system used internally for optimisations
(with a lazy RDF/XML parse on any RDF read operation when the serial isn't up to date). Changes
could be dealt with by stripping all RDF/XML from the model, and reserialising it back out into a
standard location.