ABSTRACT
A. I Introduction Modern programs for network modelling have been designed to accept input from many different types of system (e.g. telemetry, GIS), and from any manufacturer of each different type. They achieve this 'open systems' approach by the use of standard interface formats. These are formats specified for inputting logger data (SLI), telemetry data (STI) and geographical data (SGI). In principle, it is much simpler for systems manufacturers to produce output in this standard format than for the generalpurpose program to read dozens of different formats.
