his 
on- 
Ove 
net- 
e 
te- 
he 
X- 
le- 
can be naturally represented in frames. Rules, on the oth- 
er hand, are appropriate for representing heuristic net- 
work design knowledge (e.g. in diagnosis). 
Finally, the considerations presented in this paper are 
based on a current understanding of the role of expertise 
in solving the network design problem and experiences 
made in developing CONSENS. Furthermore, these con- 
siderations were applied to a relatively small sub-task in 
network design diagnosis. The conceptualisation and 
knowledge representation issues addressed may there- 
fore not be generalisable to the entire body of network 
design expertise. For instance, the issue of spatial data 
representation and reasoning, an important element in 
network design (given that each network is indeed a spa- 
tial entity), was not dealt with in this paper. 
ACKNOWLEDGEMENTS 
The authors would like to express their appreciation to A. 
Grün, C. Fraser, H. Beyer and J. Fryer for assisting us by 
imparting their expertise and offering constructive sug- 
gestions. The project Design and Analysis of Spatial Im- 
age Sequences is sponsored by the Swiss National 
Research Program NFP23 Künstliche Intelligenz und Ro- 
botik. This support is gratefully acknowledged. 
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