Subscribing for notification when there is change(add/delete/modify) of entry/attribute

[anteneh assen]

I need applications, which uses the directory server for storage, to be able to subscribe
for notification when a specific kind entry/attribute/sub-tree is changed by another
application(the application could be same kind of application or not). SOAP (Simple Object
Access Protocol), not LDAP,  is used to send subscription request for notification and
receive the response. After the application has successfully subscribed for notification
the DS should send a notification to the app using SOAP. Is it possible to write code to
implement this feature and if yes how hard would it be? thank you