public void Modify( 
   AttributedRelationshipClassDescription attributedRelationshipClassDescription
)

public void ModifyRelationshipClass(SchemaBuilder schemaBuilder, AttributedRelationshipClassDefinition attributedRelationshipClassDefinition)
{
  AttributedRelationshipClassDescription attributedRelationshipClassDescription = new AttributedRelationshipClassDescription(attributedRelationshipClassDefinition);

  // Update the relationship split policy
  attributedRelationshipClassDescription.RelationshipSplitPolicy = RelationshipSplitPolicy.UseDefault;

  // Add field in the intermediate table
  attributedRelationshipClassDescription.FieldDescriptions.Add(FieldDescription.CreateIntegerField("RelationshipStatus"));

  // Add relationship rules based on subtypes,if available
  // Assuming origin class has subtype with code 1
  attributedRelationshipClassDescription.RelationshipRuleDescriptions.Add(new RelationshipRuleDescription(1, null));

  // Enqueue modify operation
  schemaBuilder.Modify(attributedRelationshipClassDescription);

  // Execute modify DDL operation
  schemaBuilder.Build();
}

public void ModifyAnnotationLabelAndSymbols(SchemaBuilder schemaBuilder, AnnotationFeatureClassDefinition annotationFeatureClassDefinition)
{
  AnnotationFeatureClassDescription annotationFeatureClassDescription = new AnnotationFeatureClassDescription(annotationFeatureClassDefinition);
  IReadOnlyList<CIMLabelClass> labelClasses = annotationFeatureClassDescription.LabelClasses;

  // Adding a new annotation label class 
  List<CIMLabelClass> modifiedLabelClasses = new List<CIMLabelClass>(labelClasses);
  modifiedLabelClasses.Add(new CIMLabelClass()
  {
    Name = "RedSymbol",
    TextSymbol = new CIMSymbolReference
    {
      Symbol = new CIMTextSymbol()
      {
        Angle = 45,
        FontType = FontType.Type1,
        FontFamilyName = "Arial",
        FontEffects = FontEffects.Normal,
        HaloSize = 2.0,

        Symbol = new CIMPolygonSymbol { SymbolLayers = new CIMSymbolLayer[] { new CIMSolidFill { Color = CIMColor.CreateRGBColor(255, 0, 0) } }, UseRealWorldSymbolSizes = true }
      },
      MaxScale = 0,
      MinScale = 0,
      SymbolName = "TextSymbol-RED"
    },
  });

  // Adding a  new symbol
  annotationFeatureClassDescription.Symbols.Add(new CIMSymbolIdentifier()
  {
    ID = 1001,
    Name = "ID_10001",
    Symbol = new CIMTextSymbol()
    {
      Angle = 43,
      FontEffects = FontEffects.Subscript,
      FontType = FontType.TTOpenType,
      FontStyleName = "Regular",
      FontFamilyName = "Tahoma",
      TextCase = TextCase.Allcaps
    }
  });

  // Modify annotation feature class 
  AnnotationFeatureClassDescription modifiedAnnotationFeatureClassDescription = new AnnotationFeatureClassDescription(annotationFeatureClassDescription.Name, annotationFeatureClassDescription.FieldDescriptions, annotationFeatureClassDescription.ShapeDescription, annotationFeatureClassDescription.GeneralPlacementProperties, modifiedLabelClasses);

  // Enqueue modify
  schemaBuilder.Modify(modifiedAnnotationFeatureClassDescription);

  // DDL execute
  schemaBuilder.Build();

}