java.lang.IllegalStateException: Cannot modify resource set without a write transaction
at org.eclipse.emf.transaction.impl.TransactionChangeRecorder.assertWriting(TransactionChangeRecorder.java:348)

protected void assertWriting() {
		InternalTransaction tx = domain.getActiveTransaction();
		
		if ((tx == null) || tx.isReadOnly() || (tx.getOwner() != Thread.currentThread())) {
			synchronized (domain) {
				tx = domain.getActiveTransaction();

				// the transaction could be null now if it completed before we
				//    synchronized on the domain
				if (tx != null) {
					tx.abort(new Status(
						IStatus.ERROR,
						EMFTransactionPlugin.getPluginId(),
						EMFTransactionStatusCodes.CONCURRENT_WRITE,
						Messages.concurrentWrite,
						null));
				}
			}
			
			IllegalStateException ise = new IllegalStateException(
				Messages.noWriteTx);
			
			Tracing.throwing(TransactionChangeRecorder.class, "assertWriting", ise); //$NON-NLS-1$
			
			throw ise;
		}
	}