Magento

When upgrading from 0.8.16100 to 0.8.17240, some custom code started giving me some errors that it couldn’t find the model for ‘catalog/product_link_attribute’.  I was trying to find the class Mage_Catalog_Model_Product_Link_Attribute or its equivalent and have had no luck.  Could anyone please help me out?  How do I get the model for a product link attribute in 0.8.17240?  Thanks in advance.