Rewrites config

config.xml

<?xml version="1.0" encoding="UTF-8"?>
<config>
    <modules>
        <Training_Practice>
            <version>0.1.0.0</version>
        </Training_Practice>
    </modules>
    <global>
        <models>
            <!-- Mage::getModel('catalog/product') -->
            <catalog>
                <rewrite>
                    <product>Training_Practice_Model_Catalog_Product</product>
                </rewrite>
            </catalog>
            <!-- Mage::getResourceModel('catalog/product') -->
            <catalog_resource>
                <rewrite>
                    <product>Training_Practice_Model_Resource_Catalog_Product</product>
                </rewrite>
            </catalog_resource>
            <!-- Mage::getModel('customer/customer') -->
            <customer>
                 <rewrite>
                     <customer>Training_Practice_Model_Customer_Customer</customer>
                 </rewrite>
            </customer>
            <!-- Mage::getModel('sales/order_item') -->
            <sales>
                <rewrite>
                    <order_item>Training_Practice_Model_Sales_Order_Item</order_item>
                </rewrite>
            </sales>
        </models>
        <blocks>
            <!-- <block type="catalog/product_view" ... /> -->
            <catalog>
                <rewrite>
                    <product_view>Training_Practice_Block_Catalog_Product_View</product_view>
                </rewrite>
            </catalog>
            <!-- <block type="cms/block" ... /> -->
            <cms>
                <rewrite>
                    <block>Training_Practice_Block_Cms_Block</block>
                </rewrite>
            </cms>
        </blocks>
        <helpers>
            <!-- Mage::helper('customer/address') -->
            <customer>
                <rewrite>
                    <address>Training_Practice_Helper_Customer_Address</address>
                </rewrite>
            </customer>
            <!-- Mage::helper('sales') or Mage::helper('sales/data') -->
            <sales>
                <rewrite>
                    <data>Training_Practice_Helper_Sales_Data</data>
                </rewrite>
            </sales>
        </helpers>
    </global>
</config>