public List<Table> loadTablesMwe() throws Exception {
		
		String pathfolder = ResourcesPlugin.getWorkspace().getRoot().getProject(projectName).getLocation().toOSString();
		
		
		Reader reader = new Reader();
		
		reader.addRegister(new AGStandaloneSetup());
		
		UriFilter filter = new UriFilter() {
		
			@Override
			public boolean matches(URI uri) {
				if (uri != null) {
                                        //I filter by file extension
					if( Services.isProcedureSource(uri.toFileString()) ||
						Services.isSDTSource(uri.toFileString())
						)
						return false;
				}
				return true;
			}
		};
		reader.setUriFilter(filter);
		reader.addPath(pathfolder);
		
		SlotEntry se = new SlotEntry();
		se.setSlot("tables");
		
                //What should be here in Type? The language name? the EObject type?
		se.setType("Table");
		
		IWorkflowContext ctx = new WorkflowContextImpl();
		
		
		reader.setSkipOnErrors(true);
		
		try {
			reader.invoke(ctx);
		} catch(WorkflowInterruptedException e) {
			System.out.println(e.getMessage());
			return null;
		}


		List<Table> tables = (List<Table>) ctx.get("tables");
		return tables;
	}

java.lang.NullPointerException
	at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:180)
	at com.google.common.collect.ImmutableMultimap$Builder.put(ImmutableMultimap.java:149)
	at com.google.common.collect.ImmutableListMultimap$Builder.put(ImmutableListMultimap.java:161)
	at com.google.common.collect.Multimaps.index(Multimaps.java:1223)
	at org.eclipse.xtext.mwe.Validator.groupByURI(Validator.java:148)
	at org.eclipse.xtext.mwe.Validator.appendMessages(Validator.java:121)
	at org.eclipse.xtext.mwe.Validator.toString(Validator.java:104)
	at org.eclipse.xtext.mwe.Validator.validate(Validator.java:88)
	at org.eclipse.xtext.mwe.Reader.invokeInternal(Reader.java:165)
	at org.eclipse.emf.mwe.core.lib.AbstractWorkflowComponent.invoke(AbstractWorkflowComponent.java:126)
	at org.eclipse.emf.mwe.core.lib.Mwe2Bridge.invoke(Mwe2Bridge.java:34)
	at org.eclipse.emf.mwe.core.lib.AbstractWorkflowComponent.invoke(AbstractWorkflowComponent.java:201)
	at altagracia.parser.XtextResourceLoader.loadTablesMwe(XtextResourceLoader.java:454)
	at altagracia.plugin.popup.actions.Test.run(Test.java:35)
	at org.eclipse.ui.actions.ActionDelegate.runWithEvent(ActionDelegate.java:70)
	at org.eclipse.ui.internal.PluginAction.runWithEvent(PluginAction.java:241)
	at org.eclipse.jface.action.ActionContributionItem.handleWidgetSelection(ActionContributionItem.java:584)
	at org.eclipse.jface.action.ActionContributionItem.access$2(ActionContributionItem.java:501)
	at org.eclipse.jface.action.ActionContributionItem$5.handleEvent(ActionContributionItem.java:411)
	at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1258)
	at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3586)
	at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3207)
	at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2696)
	at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2660)
	at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2494)
	at org.eclipse.ui.internal.Workbench$7.run(Workbench.java:674)
	at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
	at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:667)
	at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
	at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:123)
	at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:344)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:616)
	at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:622)
	at org.eclipse.equinox.launcher.Main.basicRun(Main.java:577)
	at org.eclipse.equinox.launcher.Main.run(Main.java:1410)
	at org.eclipse.equinox.launcher.Main.main(Main.java:1386)

		result.putAll(Multimaps.index(Arrays.asList(diagnostic), new Function<MWEDiagnostic, URI>() {
			public URI apply(MWEDiagnostic from) {
				Issue issue = (Issue) from.getElement();
				URI uriToProblem = issue.getUriToProblem();
				return uriToProblem != null ? uriToProblem.trimFragment() : null;
			}
		}));