we're currently building a prototype which uses Graphiti in combination with http://komma.sourceforge.net/ to create graphical editors for system structures.
In addition to Graphiti's diagram data, our business objects are stored as RDF data in separate resources.
Since KOMMA enables the mapping between Java objects and RDF, it could also be possible to store the PictogramElements as RDF.
A prerequisite to do this is to remove all EMF specific code from the org.eclipse.graphiti.mm plugin and introduce some interfaces that encapsulate the notification and persistence logic.
Now the question is, will the Graphiti team support such developments in the future?