Magento Modules Development: Overriding

mage\app\etc\modules\My_Module.xml

<?xml version="1.0"?>

<config>
    <!--
        <global>
            <modules>
                <catalog>
                    <class></class>
                    <rewrite></rewrite>
    -->
    
    <global>
        <blocks>
            <catalog>
                <rewrite>
                    <product_view>My_Module_Block_Product_View</product_view>
                </rewrite>
            </catalog>
        </blocks>
        <helpers>
            <sales>
                <rewrite>
                    <data>My_Module_Helper_Data</data>
                </rewrite>
            </sales>
            <customer>
                <rewrite>
                    <address>My_Module_Helper_Address</address>
                </rewrite>
            </customer>
        </helpers>
        <models>
            <catalog>
                <rewrite>
                    <product>My_Module_Model_Product</product>
                </rewrite>
            </catalog>
            <catalog_resource>
                <rewrite>
                    <product>My_Module_Model_Product_Resource_Model</product>
                </rewrite>
            </catalog_resource>
        </models>
    </global>
</config>

mage\test.php

<?php

    include 'app/Mage.php';
    Mage::app();
    
//    $obj = Mage::getModel('catalog/product')->load(1);
//    var_dump( $obj->getName() );

//    $obj = Mage::app()
//            ->getLayout()
//            ->createBlock('catalog/product_view');
    
//    $obj = Mage::getResourceModel('catalog/product');
    
//    $obj = Mage::helper('sales');
    
    $obj = Mage::helper('customer/address');
    
    echo get_class( $obj );

magento\app\code\local\My\Module\Block\Product\View.php

<?php

class My_Module_Block_Product_View 
    extends Mage_Catalog_Block_Product_View {
    
}

magento\app\code\local\My\Module\etc\config.xml

<?xml version="1.0"?>
<config>
	<default>
		<some>
			<random>
				<xpath>This is a value.</xpath>
			</random>
		</some>
	</default>
</config>

magento\app\code\local\My\Module\Helper\Address.php

<?php

class My_Module_Helper_Address extends Mage_Customer_Helper_Address {
    
}

magento\app\code\local\My\Module\Helper\Data.php

<?php

class My_Module_Helper_Data extends Mage_Sales_Helper_Data {
    
}

magento\app\code\local\My\Module\Model\Product.php

<?php

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 * Description of Product
 *
 * @author Bangonkali
 */
class My_Module_Model_Product extends Mage_Catalog_Model_Product {
    public function getName() {
        $name = parent::getName();
        return strtoupper($name);
    }
}

?>

magento\app\code\local\My\Module\Model\Product\Resource\Model.php

<?php

class My_Module_Model_Product_Resource_Model
    extends Mage_Catalog_Model_Resource_Product {
    
}