Implementation of an application rule for an application to be accessed by a User Equipment, UE, in a user session in a Service Based Architecture, SBA, domain in a core network of a telecommunications system is disclosed. The SBA, among others, comprises a Policy Control Function, PCF (6), an Application Function, AF (5), and a Session Management Function, SMF (9). The method comprising the steps of receiving, by the PCF (6), an application rule comprising an AF Identifier, AF-ID, identifying the application rule, an Application Identifier, App-ID, identifying the application, and at least one service requirement for processing the application in the SBA domain. The PCF (6) instructing the SMF (9) to execute the at least one service requirement to all present and future user sessions pertaining to the respective application. Complementary methods of supporting the execution of the application rule and devices are also presented.