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CASSM project



 

Introduction p 2: What CASSM offers

CASSM helps the analyst to think about system and user representations in a structured and rigorous way.

Example

We applied CASSM to London Ambulance Service's call-handling. We found two different concepts of "call":

  • emergency call (someone dialling '999' to report an incident); this concept has attributes such as caller line identifier, nature of incident as reported, caller location, etc.
  • incident – with properties such as number of casualties, location, type of incident, etc.

Incidents in public places, such as road traffic accidents or train crashes, can generate dozens or even hundreds of emergency calls for a single incident.

PROBLEM ..... at that time the ambulance controllers had a computer system that forced them to process emergency calls rather than incidents, requiring them to specify which resources (ambulances etc.) had been deployed to each phone call. So they had to repeat identical information dozens or hundreds of times. At a busy time, this might delay their response to some other incident ...

Obvious with hindsight, of course. But it wasn't obvious at the time: it was the structured, rigorous CASSM analysis that helped tease these two concepts apart.

In more detailed working, CASSM can support thinking about structural misfits such as viscosity ... but that topic demands too much detail for an overview, and is left to the tutorial.

[ next page : the 'misfit' concept]

This page last modified 26 February, 2010 by Ann Blandford

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