@Inject
private ResourceDescriptionsProvider resourceDescriptionsProvider;
public boolean isReferenced(final EObject object) {
		if (object.eIsProxy()) {
			return false; 
		final IResourceDescriptions descriptions = getResourceDescriptions(object);
		if (descriptions == null) {
			LOG.error("'resourceDescriptions' wurden nicht gefunden.", new IllegalStateException());
		} else {
			final URI objectUri = EcoreUtil.getURI(object);
			if (objectUri != null) {
				final Iterable<IResourceDescription> allResourceDescriptions = descriptions
						.getAllResourceDescriptions();
				for (final IResourceDescription rd : allResourceDescriptions) {
					for (final IReferenceDescription refd : rd.getReferenceDescriptions()) {
						final URI targetEObjectUri = refd.getTargetEObjectUri();
						if (objectUri.equals(targetEObjectUri)) {
							return true;
						}
					}
				}
			}
		}
		return false;
	}

	public IResourceDescriptions getResourceDescriptions(final EObject object) {
		Resource resource = object.eResource();
		if (resource != null) {
			return resourceDescriptionsProvider.getResourceDescriptions(resource);
		} else {
			//TODO
return null;
		}
	}

import java.util.HashSet;
import java.util.Set;

import javax.inject.Inject;

import org.eclipse.emf.ecore.EClass;
import org.eclipse.emf.ecore.EObject;
import org.eclipse.emf.ecore.resource.ResourceSet;
import org.eclipse.emf.ecore.util.EcoreUtil;
import org.eclipse.xtext.resource.IContainer;
import org.eclipse.xtext.resource.IEObjectDescription;
import org.eclipse.xtext.resource.IResourceDescription;
import org.eclipse.xtext.resource.IResourceDescriptions;
import org.eclipse.xtext.resource.impl.ResourceDescriptionsProvider;

public class Util {
	@Inject
	private IContainer.Manager containerManager;

	@Inject
	private ResourceDescriptionsProvider rdp;

	public <T extends EObject> Set<T> getFromIndex(EObject ctx, final EClass type) {
		final Set<T> result = new HashSet<T>();

		ResourceSet rs = ctx.eResource().getResourceSet();

		final IResourceDescriptions resDesc = rdp.getResourceDescriptions(rs);

		final IResourceDescription resourceDescription = resDesc.getResourceDescription(ctx.eResource().getURI());
		if (resourceDescription == null) {
			return result;
		}
		final IContainer container = containerManager.getContainer(resourceDescription, resDesc);

		for (final IResourceDescription indexedResourceDesc : container.getResourceDescriptions()) {
			for (final IEObjectDescription ieod : indexedResourceDesc.getExportedObjectsByType(type)) {
				if (ieod.getEClass().eIsProxy()) {
					continue;
				}
				EObject proxy = ieod.getEObjectOrProxy();
				rs.getResource(ieod.getEObjectURI().trimFragment(), true);
				proxy = EcoreUtil.resolve(proxy, rs);
				if (!proxy.eIsProxy()) {
					result.add((T) proxy);
				}
			}
		}
		return result;
	}

}