class mapping between magento 1 and magento2

[lifelin]

As some mangeto1 class is not existing in magento2,such as class "Mage_Sales_Model_Quote_Address_Total_Tax",so I want to not if there has document about class mapping between magento 1 and magento2 for developer,because I want to know which class in magento2 replace class "Mage_Sales_Model_Quote_Address_Total_Tax" of magento1.Hope get help,thanks!

[Dmitry_Fedyuk]

A map between Magento 2 and Magento 1.x names: https://mage2.pro/t/51

[lifelin]

Thank you for you answer,but I see some class are in unmapped_classes.json,this  means  these class were removed or abandoned by magento2?If so,what can we do when migrate the 3rd extension which use these unmapped classes from magento1.x to magento2?