Topic: Does extending core classes fall under the extension framework?

Just a little confused after reading the description of the FA extensions framework (https://frontaccounting.com/fawiki/index.php?n=Devel.Extensions).  Could someone clarify how the desired modification described below will fit into the extension framework?

I am not looking to add a new menu option or tab, but simply extend existing core functionality.  Specifically, after a purchase order is processed/received I would like to add an additional call to a new function.  Shouldn't matter what this new function does, but in my case it will be using cURL to update 3rd party s/w.

Will a mod like this (true class extension) fit into the FA extension framework and, if so, which one (plugin or module)? Or should I just modify the appropriate core class directly and track changes via source control (SVN, CVS, etc.)?

Re: Does extending core classes fall under the extension framework?

Anybody?

...I'm under the impression that if I want to extend core classes I should just do so in the original code.  That there is no extension framework for extending core functionality.  Is this true?

Re: Does extending core classes fall under the extension framework?

I'm not sure what you mean by 'extending core clases'. I guess the right solution for you is using db_postwrite() hook defined in your extension hook class derived from general hooks class (see includes/hooks.inc). If this method is defined, it is called just after transaction is stored in database - see add_po() function in purchasing/includes/po_db.inc.

Janusz