ChildModelOne.php

class ChildModelOne extends ParentModel {
}

ChildModelTwo.php

class ChildModelTwo extends ParentModel {
}

generate_yaml.php

// Rig up Doctrine auto loader
spl_autoload_register(array("Doctrine", "autoload"));
spl_autoload_register(array("Doctrine_Core", "modelsAutoload"));

// Instantiate a manager instance and connection
$_DOCTRINE_MANAGER = Doctrine_Manager::getInstance();
$_DOCTRINE_CONNECTION = Doctrine_Manager::connection("mysql://" . DB_USER . ":" . DB_PASS . "@" . DB_HOST . "/" . DB_NAME);

// Configure Doctrine
$_DOCTRINE_MANAGER->setAttribute(Doctrine_Core::ATTR_VALIDATE, Doctrine_Core::VALIDATE_ALL);
$_DOCTRINE_MANAGER->setAttribute(Doctrine_Core::ATTR_EXPORT, Doctrine_Core::EXPORT_ALL);
$_DOCTRINE_MANAGER->setAttribute(Doctrine_Core::ATTR_MODEL_LOADING, Doctrine_Core::MODEL_LOADING_CONSERVATIVE);
$_DOCTRINE_MANAGER->setAttribute(Doctrine_Core::ATTR_AUTO_ACCESSOR_OVERRIDE, true);
$_DOCTRINE_MANAGER->setAttribute(Doctrine_Core::ATTR_AUTOLOAD_TABLE_CLASSES, true);

// Enable model auto loading
Doctrine_Core::loadModels(APP_DIR . "/models");

// Generate a YAML schema of the models
Doctrine_Core::generateYamlFromModels(APP_DIR . "/schema/schema.yml", APP_DIR . "/models");

ParentModel.php

class ParentModel extends Doctrine_Record {
  public function setTableDefinition() {
    $this->hasColumn("test", "integer");
    $this->setSubclasses(array(
      "ChildModelOne" => array("type" => 1),
      "ChildModelTwo" => array("type" => 2)
    ));
  }
}

schema.yml

Parent:
  connection: 0
  tableName: parent
  columns:
    id:
      type: integer(8)
      autoincrement: true
      primary: true
    test: integer(8)
ChildModelOne:
  connection: 0
  tableName: child_model_one
  columns:
    id:
      type: integer(8)
      autoincrement: true
      primary: true
    test: integer(8)
ChildModelTwo:
  connection: 0
  tableName: child_model_two
  columns:
    id:
      type: integer(8)
      primary: true
    test: integer(8)