Why Software Systems Fail
Uploaded by panchamb on May 05, 2000
1.0 Introduction
In this report I will be concentrating on the failure of software systems. To understand why software systems fail we need to understand what are software systems. Software systems are a type of information system. This is because a software system is basically a means for hardware to process information. Flynn’s definition of an information system is:
"An information system provides procedures to record and make available information, concerning part of an organization, to assist organization-related activities."
Humans have been processing information manually for thousands of years, but with the vast increase of demand for knowledge this century has meant that a new method of information processing has been needed. Software systems have provided a new means that is much faster and efficient. As a result a huge number of organisations have become software dependent. Some of these systems are used to safeguard the lives of many people. This means that if these systems were to fail they could lead to devastating consequences. Here are some examples of where software systems are used heavily and could be very dangerous if they were to fail - aviation, hospitals, space exploration, nuclear power stations and communications. I will be looking at some examples of actual software failure in these fields to explain the reasons why systems fail.
2.0 Reasons for Systems Failure
If software systems failure can be so dangerous why can they not be completely eliminated? According to Parnas, "The main reason is that software can never be guaranteed to be 100% reliable. Software systems are discrete-state systems that do not have repetitive structures. The mathematical functions that describe the behaviour of software systems are not continuous, and traditional engineering mathematics do not help in their verification." In other words some software can be so large that thorough testing can be almost impossible and so bugs in the software can go unnoticed. An example of this was when an Atlas-Agena rocket veered off-course when it was ninety miles up. Ground control had to destroy the $18.5 rocket. The reasons for this - a missing hyphen. However there are many more reasons for software systems failure, and most of them are due to human negligence that leads to software failure. There are two types of software systems failure. These are in the design stage of...