Feature Interaction Filtering and Detection with Use Case Maps and LOTOS

Jameleddine Hassine

Thesis submitted to the school of graduate studies and research in
partial fulfillment of the requirements for the degree of

Master of Computer Science Under the auspices of the Ottawa-Carleton
Institute of Computer Science

University of Ottawa, Ottawa, Ontario, Canada February 2001

Abstract

Telephony systems have evolved from the Plain Old Telephony System
providing only the basic functionality of making phone calls, to
sophisticated systems in which many features have been introduced,
providing network subscribers more control on the call establishment
process. However, these facilities are confronted with a major obstacle
known as the feature interaction problem.

A feature interaction occurs when at least one feature is prevented from
performing its functionality or when the system functions incorrectly
due to the presence of features.  In the first part of the thesis, we
present a model for describing telephony features at the requirements
stage. This model is built using the Use Case Maps Notation (UCM). Based
on this model, we propose a method to filter feature interactions at
the requirements stage. This preliminary evaluation allows the detection
process to focus on feature combinations where interactions are possible
and therefore reduces the cost of the detection process.

In the second part of the thesis, a Feature Interaction Detection System
is developed for detecting feature interactions between switch based
and IN features. This method aims to detect interactions occurring at
the abstract specification level and resulting in violation of feature
properties. This technique in based on the Formal Description technique
LOTOS and uses Abstract Data Types to detect those violations. Our method
detects feature interaction by executing the system specification. The
designer can reach those interaction points either by a step by step
execution or using the goal oriented execution technique.

It is concluded that UCM and LOTOS are useful in specifying the telephony
system with features and for detecting feature interactions at the
abstract specification level.