The present invention is aimed to provide a mechanism whereby a Public Service Identity identifying a service, which runs in an application service, may be created in a network both dynamically by the application server and statically by an O & M system, the means and method for the dynamic creation harmonizing with those for the static creation, and allowing a similar behavior of the network with minimum impact when the service is invoked. Therefore, the present invention provides a new method, a new central entity in the network, and enhanced Home Subscriber Server and application server, all co-operating to carry out the different embodiments for the invention.