System platform for a communication system

In a telecommunication system providing subscriber services and having an object oriented system platform containing a number of function layers, one layer with operating system functions, an application platform located thereon and containing telecommunication abstractions in the form of resource objects, and thereupon an uppermost layer containing desired applications in the form of base and supplementary functions which provide base and supplementary services,

• a method for modifying and extending the subscriber services, comprising the steps of
• providing in the uppermost layer base objects being object types implementing base functions which may need to be extended in the future, and being designed for a specific task that can be performed with a minimum of coordination with other base objects, and
• extension objects being object types implementing extension functions providing extensions to the base functions and enabling addition of new services and modification and extension of existing services without changing the software of a system that has already been implemented and supplied, while designing the extension objects for enabling introduction of extensions into a system in operation which are dynamically bound to a base object to be modified, and addition and removal, in runtime, of modifications of the system in a generic way without programming a specific support for activating/deactivating each extension,
• defining the behavior of included base and extension object types by describing the behavior of each included method as a finite state machine consisting of a finite number of states and transitions between these states,
• executing in said transitions the code as transition actions and
• adding the extensions at said states for taking over the execution control in an extension point and return the control to another one, or the same extension point in the same method.