Evan H. Magill

Feature interaction: a critical review and considered forecast

The state of the art of the field of feature interactions in telecommunications services is reviewed, concentrating on three major research trends: software engineering approaches, formal methods, and on line techniques. Then, the impact of the new, emerging architectures on the feature interaction problem is considered. A forecast is made about how research in feature interactions needs to readjust to address the new challenges posed by the emerging architectures.

Learning to detect and avoid run-time feature interactions in intelligent networks

The Intelligent Network (IN) allows rapid changes in the services provisioned and their functionality. Services may be supplied by different service providers, making it unlikely that all service specifications will be available for examination by any single agency. Approaches to handle feature interaction problems must be able to operate within these constraints. Work by the authors has produced a generic run time feature interaction manager (FIM) concept to manage feature interactions in a live network. It monitors features as black boxes, learns their correct behavior and uses this to determine when feature interactions have occurred. The paper describes and compares experiences using three different techniques to realize the proposed approach. These are: state sequence monitoring, artificial neural networks (ANN), and rule based monitoring which also includes integrated generic resolution approaches. The paper explores the design alternatives with the various techniques, and reports on the results obtained from experimentation.

Hybrid approach to software interworking problems: managing interactions between legacy and evolving telecommunications software

Interworking problems between software services arise for a number of reasons; they may occur because the services, or their component parts, have evolved to fulfil different roles from the originally intended ones, resulting in conflicting requirements. Alternatively, the services themselves may be undocumented, poorly understood, or required to interwork with services from third party legacy systems. Interworking problems are difficult to predict and detect, as well as to resolve in an acceptable manner. The problems are particularly acute in the telecommunications domain with its supplementary concerns of real−time, distributed control and data, high reliability, rapid evolution, and a deregulated market that is encouraging multiple service providers. Approaches to interworking problems may be characterised as being either online or offline, formally or pragmatically/experimentally based. While numerous approaches have been developed, there have been very few attempts to combine formally based and online approaches to produce a technique. The research goal is to develop such a technique because experience with other combinations has led to the belief that they are not sufficient to deal with the interworking problems of complex, evolving software systems, as common in telecommunications. This is particularly the case for systems which also have to interwork with third party and legacy code: a hybrid approach which combines both online and formally based approaches promises to address problems which have proven very difficult to resolve with other techniques. The paper outlines a hybrid approach based on a transactional technique with rollback capability. While the approach described is applied specifically to telecommunications services software, many aspects of the approach are applicable to other software domains which exhibit similar characteristics of real-time, event driven operation, such as control systems.

Experiences modelling and using formal object-oriented telecommunication service frameworks

Abstract This paper describes experiences in using SDL and its associated tools to create telecommunication services by producing and specialising object-oriented frameworks. The chosen approach recognises the need for the rapid creation of validated telecommunication services. It introduces two stages to service creation. Firstly a software expert produces a service framework, and secondly a telecommunications `business consultant specialises the framework by means of graphical tools to rapidly produce services. Here the focus is given to the underlying technology required. In particular, the advantages and disadvantages of SDL and tools for this purpose are highlighted.

Theory and practice of enhancing a legacy software system

Telephone switching systems are an interesting class of legacy system as they are complex, distributed and safety critical. As with most legacy systems, a simple replacement is impossible (or at least impractical), therefore changes in business practice and technology have induced a perpetual evolution of telephone switching systems.

Engineering of interworking TINA-based telecommunication services

This paper describes a service creation approach being developed in the EU funded ACTS TOSCA (TINA open service creation architecture) project to rapidly develop validated TINA based multimedia telecommunications services. The approach is based around object-oriented software frameworks in SDL which are specialized towards services by means of graphical paradigm tools. Further, in TOSCA, the need for service interworking across service provider domains via federation has been recognized in order to allow users to join service sessions offered by providers they are not customers of. However, service interworking may cause undesired behavior-the so called service interaction phenomenon. This paper focuses on this issue and the underlying technology of the service creation approach with emphasis on how service federation has been implemented.

The network operator's perspective: detecting and resolving feature interaction problems

Abstract In many countries regulatory pressure is likely to force the incumbent network operators to open up their networks to other service providers. The Intelligent Network is a catalyst to allow this to be technically feasible. Clearly the network operators must address feature interaction detection within the Intelligent Network. As the size and penetration of intelligent networks (IN) increases, and the need to interwork different IN platforms, private business networks, virtual private networks and residential network services becomes greater, these issues will have to be addressed if the process of designing and provisioning new services is not to remain difficult and costly. This paper explores some of these issues from the network operators perspective and considers the impact and restrictions that they impose on feature interaction management techniques. Within these constraints a new practical approach proposed by the authors is outlined, based on the international ITU-T IN recommendations (CS-1). The approach proposes initially capturing “correct” (or signature) feature behaviour in a test environment. The signatures are then used at run-time to monitor feature behaviour and to detect deviations from the correct behaviour. The detection approach includes a predictive element, which allows some types of interaction to be avoided. In cases where this is not possible, a default call recovery approach is applied which restores the call to a known state.