Method and arrangement for testing services in a telecommunications system

#The present invention relates to a method and arrangement for trying out in advance prerequisites for introducing new services in a telecommunications system. When introducing new services, supplementary services, in a complex system, for example a telecommunications system, it is an advantage and in practice a necessity that, with the development of each new service, one only needs to take into consideration how the new service will function together with a basic part of the existing system (base system) or together with the base system and some service developed earlier and on which the new service is intended to build. Not to have to take into consideration supplementary services developed earlier and any services which are developed in parallel reduces the development so significantly that this can be considered to be the normal way of attacking the problem with supplementary services.

#However, this method entails the risk that different supplementary services introduced interfere with one another in a manner which cannot be predicted in a design, so-called interservice interference, through combination effects between the different supplementary services.

#A complete development is traditionally made to end when each service by itself is installed in the existing telecommunications system. It has been attempted to attack the problem of interservice interference by carrying out limited manual analyses, as a rule based on the designer's own earlier experiences. Alternatively, the interference problems have not been uncovered until the operation of the resulting system, which results in the work for correcting the problem being much harder.

#The invention will now be described in detail with reference to the following drawing, the only figure of which is a block diagram of the arrangement according to the invention.

#The invention builds on the fact that the telecommunications system in which the new services will be introduced, that is to say the base system, is described by a formal specification language. This is an established technique and there are a number of formal languages which are used for the purpose. The services which will be supplied are described by the same language as separate supplements to the base system description. The supplementary services can be analysed separately for verifying that they will function together with the base system in the intended way. The different services thus described can then be brought together to form a description of the total resultant system. The system can then be analysed by known analysis techniques, for example reachability analysis, in order to identify problems which could occur as a consequence of combination effects between supplementary services. The reachability analysis creates a model in the form of a tree with action/condition chains. The result of the analysis is a list of conditions which lead to malfunction situations. The list is an aid for finding problems with interservice interference.

#The Figure describes a preferred embodiment of the invention. The designer uses a service editor for defining a new service in the system. There are graphic editors for interactive design of services. These provide the possibility to define a service in a user-friendly way, expressed in service descriptions which consist of modules or blocks (SIB, service independent building block). The CCITT definition of the modules is expressed as a translation from a service description containing modules into SDL (specification description language). Each module is defined with the aid of a translation to a fragment of a SDL process.

#The specification language generator is a SDL code generator which takes a description and translates it into SDL in accordance with translation rules which are defined in the CCITT recommendations.