All methods of change notification are based on a periodic queries of database - is it true?

Dear Gurus!

I need in silverlight application system of notification about changes in mssql database.

I have try to use service broker, but met the problem - when service wait notification - ria services query are blocking.

Maybe I just made ​​a mistake somewhere.

I met statement that "All methods of change notification are based on a periodic queries of database" .

1. Is it true? 

2. Is it right way to use service broker for a such task?

3. Can mssql  itself to notify the  server application about  changes, say using an interrupt when the some trigger is fired?

Thanks in advance!