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1 Introduction 
Modern integrated navigation systems (INS) offer a large number of functions which are necessary to 
fulfil the tasks of navigational operation. With the increasing degree of integration, however, the in 
stances of interdependence and interlinking among the functions are also increasing. This makes test 
ing of these systems in particular more difficult, since the growing number of Interactions between the 
system components means that the number of possible system states becomes very large. An addi 
tional impeding factor is that implementation of the different functions - depending on the particular 
manufacturer or equipment philosophy - may differ very widely. 
Within the framework of this study, therefore, an approach was selected which enables an equipment- 
dependent description of the functional properties of INS. In part A of this study a catalogue of the func 
tions of navigational operation is presented, which serves as a basis for the functional description of 
INS. In this catalogue, the functions are already classified in levels in a hierarchy governed by logic and 
content. The listing of the functions moreover follows the following structure: 
Task areas are derived from a definition of the global process task. The areas involved here are voyage 
planning, voyage execution and dealing with unplanned incidents. 
To each task area are assigned tasks which are defined by a clear action purpose. 
For each task are identified the functionalities and functions necessary to achieve the action purposes. 
These moreover follow a hierarchical structure breaking down into overriding units (functionalities on 
several levels) and elementary individual functions. The particular level considered is at the same time 
a measure of the degree of abstraction (the higher the level, the greater the degree of abstraction). 
For the functions identified in the course of the analysis, the particular input and output information nec 
essary or supplied in each case has been listed. Along with a hierarchical structure of the functionalities 
and functions, the function catalogue thus likewise contains a list of the information flows belonging to 
each function. 
The aim of this report, starting from the functional analysis represented in part A, is to develop a model 
of the process of integrated navigation. This model is intended to serve as a reference for the derivation 
of test specifications for integrated navigation systems. With the aid of the model it is possible to identify 
instances of functional dependence and resultant error chains. On the basis of the functionalities, func 
tions and information flows identified in part A, a “three-dimensional network” is developed which on 
several abstraction levels represents the information flows between the functional units present in the 
INS. 
In the following section, the approach used here for the development of the functional model Is pre 
sented. This approach is based on the “structured analysis”. This involves a formalised method for the 
description of existing systems or systems to be developed, which is chiefly used for software develop 
ment [1], [2], [3]. The different description forms for differing aspects of the model and their syntax are 
explained. The aim is to facilitate an understanding of the functional model contained in the annex to 
this report.