Unformatted text preview: incorrect information being passed back to the system. Numerous technical problems with the system, including: Failure to identify all duplicated calls; Lack of prioritisation of exception messages; Exception messages and awaiting attention queues scroll off top of screen. Poor interface between crews, MDTs & the system Unreliability, slowness and operator interface Ian Sommerville 2004 Slide 13 Software Engineering Case Studies Configuration changes
Implementation of the system on 26 October involved a number of significant changes to CAC operation, in particular: Re-configuring the control room; Installing more CAD terminals and RIFS screens; No paper backup system; Physically separating resource allocators from radio operators and exception rectifiers; Going `pan London' rather than operating in 3 divisions; Using only the system proposed resource allocations; Allowing some call takers to allocate resources; Separate allocators for different call sources. Ian Sommerville 2004 Slide 14 Software Engineering Case Studies So, what happened?
Changes to CAC operation made it extremely difficult for staff to intervene and correct the system. As a consequence, the system rapidly knew the correct location and status of fewer and fewer vehicles, leading to: Poor, duplicated and delayed allocations; A build up of exception messages and the awaiting attention list; A slow up of the system as the messages and lists built up; An increased number of call backs and hence delays in telephone answering.
Software Engineering Case Studies Ian Sommerville 2004 Slide 15 Why did it fail?
Technically, the system did not fail on October 26th Response times did become unacceptable, but overall the system did what it had been designed to do! Failed 3 weeks later due to a program error - this was a memory leak where allocated memory was not completely released. Management; Union; System manager; Government. It depends who you ask! Ian Sommerville 2004 Slide 16 Software Engineering Case Studies Les...
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- Fall '11
- Software engineering, Engineering Case Studies