Services_Yahoo is split up into chunks that group similar functionality. Currently there are chunks for the interfaces to Yahoo Search and to the Content Analysis functions.
Each chunk basically contains two top-level element in the source
.php file and a directory that holds
the implementation of the chunk. The file is a class that contains
only one method which implements that factory
pattern. This method dynamically loads the right file from
the related directory and returns an instance of the class that
implements the desired function.
Due to this modular layout Services_Yahoo can easily be extended when Yahoo adds new functions to their API.