Diagram diagram = Graphiti.getPeCreateService().createDiagram(diagramType, title, true);

// Create a virtual URI with a custom schema
URI uri = URI.createHierarchicalURI(VirtualURIHandler.VIRTUAL_URI_SCHEMA,
		null,
		null,
		new String[] { "diagram", id },
		null,
		null);

// Create a regular resource in the uri, in the EditingDomain that already contains the model
final Resource diagramResource = commonEditingDomain.getResourceSet().createResource(uri);				


// Add the diagram to the resource
commonEditingDomain.getCommandStack().execute(new AbstractCommand() {

	@Override
	protected boolean prepare() {
		return true;
	}

	@Override
	public void execute() {
		diagramResource.getContents().add(diagram);
	}

	@Override
	public void redo() {
	}
		
});		

String providerId = GraphitiUi.getExtensionManager().getDiagramTypeProviderId(diagram.getDiagramTypeId());		
return new DiagramEditorInput(uri, commonEditingDomain, providerId);

/** urihandler for virtual uri that writes in a pseudo /dev/null */
public class NullURIHandler implements URIHandler {

	private static final String SCHEMADEFAULT = "devnull";

	public final String schema;

	public NullURIHandler() {
		this(SCHEMADEFAULT);
	}

	public NullURIHandler(String schema) {
		this.schema = schema;
	}

	/**
	 * transforms a fileUri to a virtualuri, changing the schema
	 */
	public URI createForDiagram(URI fileUri) {
		return URI.createHierarchicalURI(schema, fileUri.authority(), fileUri.device(), fileUri.segments(), null, null);
	}

	@Override
	public boolean canHandle(URI uri) {
		return schema.equals(uri.scheme());
	}

	@Override
	public InputStream createInputStream(URI uri, Map<?, ?> options) throws IOException {
		return new InputStream() {
			@Override
			public int read() throws IOException {	return -1;}
		};
	}

	@Override
	public OutputStream createOutputStream(URI uri, Map<?, ?> options) throws IOException {
		return new OutputStream() {
			@Override
			public void write(int b) throws IOException {	}
		};
	}

	@Override
	public void delete(URI uri, Map<?, ?> options) throws IOException {	}

	@Override
	public Map<String, ?> contentDescription(URI uri, Map<?, ?> options) throws IOException {
		return new HashMap<String, String>();
	}

	@Override
	public boolean exists(URI uri, Map<?, ?> options) {
		return true;
	}

	@Override
	public Map<String, ?> getAttributes(URI uri, Map<?, ?> options) {
		return new HashMap<String, String>();
	}

	@Override
	public void setAttributes(URI uri, Map<String, ?> attributes, Map<?, ?> options) throws IOException {
		System.err.println(getClass() + ".setAttributes() not implemented ");
	}

}