Call one module model from other module model

Question

I have a design like below

I have two independent modules and one common module. That means independent module will pull information from common module.

I defined below in common module config.

<config>
    <global>
        <models>
            <services>
                <class>My_Common_Model</class>
            <services>
        <models>
    </global>
</config>

Then I tried to call a method in common module model from module_1 controller like below,

$stores = Mage::getModel('services/store')->getAvailableStore();

But is throws error like model undefined.

Then I included the common model configuration in Module_1 config.xml also. Its working now.

Is it the normal behavior? Cant we call any method in one modules model from other modules controller with defined tag in its native module itself?

I don't know how to ask this question better than this.

Module 1 Controller:

<?php
    class My_Module_UserController extends Mage_Core_Controller_Front_Action{

        function userAssignStoreAction(){

            $stores = Mage::getModel('stores/store')->getAvailableStore();

            echo $productModel;
            die;
        }
    }
?>

below is common module config file:

<config>
    <modules>
        <My_Common>
            <version>0.0.1</version>
        </My_Common>
    </modules>
    <global>
        <models>
            <stores>
                <class>My_Common_Model</class>
            </stores>
        </models
    </global>
</config>

below is module 1 config:

<global>
        <models>
            <services>
                <class>My_Module_Model</class>
            </services>
           <!-- WITHOUT BELOW DECLARATION UNABLE TO CALL COMMON MODEL METHOD FROM MODULE 1 CONTROLLER -->
            <stores>
                <class>My_Common_Model</class>
            </stores>
        </models>
    </global>

Answer 1

You should be able to call your custom model from anywhere in Magento, the same way you call any other core model e.g Mage::getModel('catalog/product')

Did you check to make sure module_1 is active?

Answer 2

Yes, What u did is perfect. Actually, This is the way magento works. Go for it. For example.

This function is defined on mage/checkout/cart.php

You can see that Mage::getModel('catalog/product') in this function. The thing is, Its okay to call other models in our own module too.

Hope you got it. Go ahead.! Cheers.

public function addOrderItem($orderItem, $qtyFlag=null)
{
    /* @var $orderItem Mage_Sales_Model_Order_Item */
    if (is_null($orderItem->getParentItem())) {
        $product = Mage::getModel('catalog/product')
            ->setStoreId(Mage::app()->getStore()->getId())
            ->load($orderItem->getProductId());
        if (!$product->getId()) {
            return $this;
        }

        $info = $orderItem->getProductOptionByCode('info_buyRequest');
        $info = new Varien_Object($info);
        if (is_null($qtyFlag)) {
            $info->setQty($orderItem->getQtyOrdered());
        } else {
            $info->setQty(1);
        }

        $this->addProduct($product, $info);
    }
    return $this;
}