/**
	 * Contributes the given {@link MModelFragment} to the application model.
	 *
	 * @param fragment
	 *            the fragment to add to the application model
	 * @param contributorURI
	 *            the URI of the element that contributes this fragment
	 * @param checkExist
	 *            specifies whether we should check that the application model
	 *            doesn't already contain the elements contributed by the
	 *            fragment before merging them
	 * @return a list of the {@link MApplicationElement} elements that were
	 *         merged into the application model by the fragment
	 */
	public List<MApplicationElement> processModelFragment(MModelFragment fragment, String contributorURI,
			boolean checkExist) {

		E4XMIResource applicationResource = (E4XMIResource) ((EObject) application).eResource();

		List<MApplicationElement> elements = fragment.getElements();
		if (elements.size() == 0) {
			return new ArrayList<>();
		}

		for (MApplicationElement el : elements) {
			EObject o = (EObject) el;

			E4XMIResource r = (E4XMIResource) o.eResource();

			if (checkExist && applicationResource.getIDToEObjectMap().containsKey(r.getID(o))) {
				continue;
			}

			applicationResource.setID(o, r.getID(o));

			if (contributorURI != null)
				el.setContributorURI(contributorURI);

			// Remember IDs of subitems
			TreeIterator<EObject> treeIt = EcoreUtil.getAllContents(o, true);
			while (treeIt.hasNext()) {
				EObject eObj = treeIt.next();
				r = (E4XMIResource) eObj.eResource();
				if (contributorURI != null && (eObj instanceof MApplicationElement))
					((MApplicationElement) eObj).setContributorURI(contributorURI);
				applicationResource.setID(eObj, r.getInternalId(eObj));
			}
		}

		return fragment.merge(application);     // <=== here the fragment gets unconditionally merged into the app model !
	}