drupal/core/modules/translation_entity/translation_entity.install

<?php

/**
 * @file
 * Installation functions for Entity Translation module.
 */

/**
 * Implements hook_schema().
 */
function translation_entity_schema() {
  $schema['translation_entity'] = array(
    'description' => 'Table to track entity translations',
    'fields' => array(
      'entity_type' => array(
        'type' => 'varchar',
        'length' => 128,
        'not null' => TRUE,
        'default' => '',
        'description' => 'The entity type this translation relates to',
      ),
      'entity_id' => array(
        'type' => 'varchar',
        'length' => 128,
        'not null' => TRUE,
        'default' => '',
        'description' => 'The entity id this translation relates to',
      ),
      'langcode' => array(
        'type' => 'varchar',
        'length' => 32,
        'not null' => TRUE,
        'default' => '',
        'description' => 'The target language for this translation.',
      ),
      'source' => array(
        'type' => 'varchar',
        'length' => 32,
        'not null' => TRUE,
        'default' => '',
        'description' => 'The source language from which this translation was created.',
      ),
      'translate' => array(
        'description' => 'A boolean indicating whether this translation needs to be updated.',
        'type' => 'int',
        'not null' => TRUE,
        'default' => 0,
      ),
    ),
    'primary key' => array('entity_type', 'entity_id', 'langcode'),
  );
  return $schema;
}

/**
 * Implements hook_install().
 */
function translation_entity_install() {
  // Assign a fairly low weight to ensure our implementation of
  // hook_module_implements_alter() is run among the last ones.
  module_set_weight('translation_entity', 10);
  language_negotiation_include();
  language_negotiation_set(LANGUAGE_TYPE_CONTENT, array(LANGUAGE_NEGOTIATION_URL => 0));
}

/**
 * Implements hook_enable().
 */
function translation_entity_enable() {
  // Translation works when at least two languages are enabled.
  if (count(language_list()) < 2) {
    $t_args = array('!language_url' => url('admin/config/regional/language'));
    $message = t('Be sure to <a href="!language_url">enable at least two languages</a> to translate content.', $t_args);
    drupal_set_message($message, 'warning');
  }
  // Point the user to the content translation settings.
  $t_args = array('!settings_url' => url('admin/config/regional/content-language'));
  $message = t('<a href="!settings_url">Enable translation</a> for <em>content types</em>, <em>taxonomy vocabularies</em>, <em>accounts</em>, or any other element you wish to translate.', $t_args);
  drupal_set_message($message, 'warning');
}