private static class DerivedStateComputer implements IDerivedStateComputer {
		
		@Inject
		@Extension
		private PBXIndex pbxIndex;

<some time later>

			// Get all existing connections from the index
			if (this.pbxIndex != null) {
				Map<QualifiedName, IEObjectDescription> existingConnections = this.pbxIndex.getVisibleExternalConnectionsDescriptions(pbxDoc);

   override bindXtextResource () {
      PBXResource
   }
   
   def Class<? extends IResourceDescription.Manager> bindIResourceDescriptionManager () {
      DerivedStateAwareResourceDescriptionManager
   }

public class PBXResource extends DerivedStateAwareResource {
		
	public PBXResource() {
		setDerivedStateComputer(new DerivedStateComputer());
	}
			
	@Override
	public void installDerivedState(boolean preIndexingPhase) {
		super.installDerivedState(preIndexingPhase);
		
	}
			
	
	private static class DerivedStateComputer implements IDerivedStateComputer {
		
		@Inject
		@Extension
		private PBXIndex pbxIndex;

		@Override
		public void installDerivedState(DerivedStateAwareResource resource, boolean preLinkingPhase) {
			
			if (!preLinkingPhase) {
	

   override bindXtextResource () {
      PBXResource
   }
   
   def Class<? extends IDerivedStateComputer> bindIDerivedStateComputer() {
      DerivedStateComputer
   }