无法检索实体配置Magento

我一直在跟踪唯一一个我不知道的错误，因为它向我显示了多长时间。

下面是我的配置.xml文件

<?xml version="1.0"?>
<config>
    <modules>
        <Maven_Questionanswer>
            <version>1.0.1</version>
        </Maven_Questionanswer>
    </modules>        
<global>
    <models>
                <questionanswer>
                    <class>Maven_Questionanswer_Model</class>
                    <resourceModel>questionanswer_resource</resourceModel>
                </questionanswer>
                <questionanswer_resource>
                    <class>Maven_Questionanswer_Model_Resource</class>
                    <entities>
                        <questionanswer>
                            <table>question</table>
                        </questionanswer>
                    </entities>
                </questionanswer_resource>
            </models>
            <resources>
                <questionanswer_setup>
                    <setup>
                        <module>Maven_Questionanswer</module>
                    </setup>
                    <connection>
                        <use>core_setup</use>
                    </connection>
                </questionanswer_setup>
                <questionanswer_write>
                    <connection>
                        <use>core_write</use>
                    </connection>
                </questionanswer_write>
                <questionanswer_read>
                    <connection>
                        <use>core_read</use>
                    </connection>
                </questionanswer_read>
            </resources>
    </global>
</config>

app/code/local/Maven/Questionanswer/Model/Question.php

 <?php
    /**
    * 
    */
    class Maven_Questionanswer_Model_Question extends Mage_Core_Model_Abstract
    {
         public function _construct()
         {
             parent::_construct();
             $this->_init('questionanswer/question');
         }
    }
    ?>

app/code/local/Maven/Questionanswer/Model/Resource/Question.php

<?php
class Maven_Questionanswer_Model_Resource_Question extends Mage_Core_Model_Resource_Db_Abstract
{
    /**
     * Initialize resource model
     *
     * @return void
     */
    public function _construct()
    {
        $this->_init('questionanswer/question', 'question_id');
    }
}
?>

magento1.9.2/app/code/local/Maven/Questionanswer/Model/Resource/Question/Collection.php

<?php
/**
* 
*/
class Maven_Questionanswer_Model_Resource_Question_Collection extends Mage_Core_Model_Resource_Db_Collection_Abstract 
{
    protected function _construct()
    {
            $this->_init('questionanswer/question');
    }
}
?>
/app/code/local/Maven/Questionanswer/sql/questionanswer_setup/install-1.0.1.php

<?php
$installer = $this;
 $installer->startSetup();
 $table = $installer->getConnection()->newTable($installer->getTable('questionanswer/question'))
    ->addColumn('question_id', Varien_Db_Ddl_Table::TYPE_INTEGER, null, array(
        'unsigned' => true,
        'nullable' => false,
        'AUTO_INCREMENT'=>true,
        'primary' => true,
        'identity' => true,
        ), 'Question ID')
    ->addColumn('username', Varien_Db_Ddl_Table::TYPE_TEXT, null, array(
        'nullable' => false,
        ), 'Username')
    ->addColumn('email', Varien_Db_Ddl_Table::TYPE_TEXT, null, array(
        'nullable' => false,
        ), 'Email username')
    ->addColumn('question', Varien_Db_Ddl_Table::TYPE_TEXT, null, array(
        ), 'Question')
    ->addColumn('product_id', Varien_Db_Ddl_Table::TYPE_INTEGER, null, array(
        ), 'Product ID')
    ->addColumn('store_id', Varien_Db_Ddl_Table::TYPE_INTEGER, null, array(
        ), 'Store ID')
    ->addColumn('status', Varien_Db_Ddl_Table::TYPE_INTEGER, null, array(
        ), 'Status')
    ->setComment('questionanswer questionanswer/question entity table');
    $installer->getConnection()->createTable($table);
$installer->endSetup();
?>

我哪里犯了错误？我只是能理解。