public List<RelationshipRuleDescription> RelationshipRuleDescriptions {get;}

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();
}