Here is an example of the problem I dont know how to solve:

Lets say you have an postgres database with table:
news[id, date, title, text], id-primary key

there are more then one users on a client side entering news using windows application (written in c#)

How can I sync data they are entering without having to use timer-based SELECT query execution ?
Is there a way in postgres to triger event when some table is updated and notify client applications, so that they could show only changed data?

Thank you very much for your suggestions,