> But i dont know what do you mean about Pull / push Methode?..
> Please...Detail... and example...
> can i read data have Change or Not ?? how?

Ok, example of pull-method of getting data: you are reading an
internet forum. You open a web-page and get all messages from a topic,
no matter whether you already read it or not. It is convenient, but you
have big internet traffic.
Example of push-method: you subscribed to this mail-list (which is
another front-end for the same forum). You'll get only new messages and
these messages contain complete information, not just link to forums's
web-page. Traffic is low, reaction time is excellent, but you must do
some additional work to gather messages into thread to get full picture.

SY, SD.