//Exercise 5 builds from Exercise 4
Lab4 lab4 = new Lab4();
XSDSchema schema = lab4.createSchema(xsdFile); //Schema from lab4

//Lets get the PurchaseOrderType complex type
XSDComplexTypeDefinition purchaseOrderType = schema.resolveComplexTypeDefinition("PurchaseOrderType");

//Lets get the model group that was created in Exercise 4
XSDModelGroup modelGroup = (XSDModelGroup)((XSDParticle)purchaseOrderType.getContent()).getContent();

/**
 * Create a global element with name="note" and type="string"
 */
XSDElementDeclaration noteElement = XSDFactory.eINSTANCE.createXSDElementDeclaration();

//Set the name to "notes"
noteElement.setName("notes");

//Set the type of notes element to string
XSDSimpleTypeDefinition stringType = schema.getSchemaForSchema().
        resolveSimpleTypeDefinition(XSDConstants.SCHEMA_FOR_SCHEMA_URI_2001,"string");
noteElement.setTypeDefinition(stringType);

//Add the global element to the root schema
schema.getContents().add(noteElement);

/**
 * Create local element with name="state", type="po:USState" and minOccurs="0"
 * Local elements have particles as parents
 */
XSDParticle localElementParticle = XSDFactory.eINSTANCE.createXSDParticle();

XSDElementDeclaration stateElement = XSDFactory.eINSTANCE.createXSDElementDeclaration();
localElementParticle.setContent(stateElement);

//Set the name to state
stateElement.setName("state");

//Set the type to USState
stateElement.setTypeDefinition(schema.resolveSimpleTypeDefinition("USState"));

//Set the minOccurs="0"
localElementParticle.setMinOccurs(0);

//Add the new particle to the modelgroup
modelGroup.getContents().add(localElementParticle);

/**
 * Create the element reference to the global element note
 */
XSDParticle elementRefParticle = XSDFactory.eINSTANCE.createXSDParticle();

XSDElementDeclaration notesRef = XSDFactory.eINSTANCE.createXSDElementDeclaration();
elementRefParticle.setContent(notesRef);

//Set the element reference to the global element notes
notesRef.setResolvedElementDeclaration(noteElement);

//Add the new particle to the modelgroup
modelGroup.getContents().add(elementRefParticle);
                
//Save the contents of the resource to the file system.
schema.eResource().save(Collections.EMPTY_MAP);