Magento calling folder path

Magento uses its own structure to call the Particular file from specific folder

For example if we want to call the the .wsdl file which is stored in the app/modulename/etc/wsdl/your.wsdl

so we will write the code in our php file like this

 public function __construct()
    { 
        $this->_ yourWsdl = Mage::getModuleDir('etc', 'Mage_ Modulename')  . DS . 'wsdl' . DS . ' Modulename'
              . DS . ' your .wsdl';  
    }

Where  

your.wsdl is the file which is stored in the app/modulename/etc/wsdl/