The UK government is spearheading a 拢10 million programme aimed at finding ways to avert catastrophic failures in large IT networks.
Some systems are now so large they are untestable, making it impossible to predict how they will behave under all circumstances. The hidden flaws could lead to crashes in critical networks like healthcare or banking systems.
The scheme has been given added urgency by the failures of power grids in the US and Italy last year. 鈥淭he system failures in terms of electricity blackouts show that patterns of unexpected and negative behaviours can arise, and when they do they are often disastrous,鈥� says the government鈥檚 chief scientist, David King. If a century-old technology like a power grid can fail, the same might easily happen to modern IT networks.
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Cancelled government IT projects plus others that have run over budget 鈥� such as tax and child benefit computer systems 鈥� cost the UK 拢1.5 billion over six years, according to a 2003 report from the Office of Government Commerce.
Now all government departments, health services and education systems across the 25 countries of the European Union are being linked to the internet. And the UK government ultimately wants many departmental IT systems connected together in the name of 鈥渏oined-up government鈥�.
But there is a real danger that such massive interconnected systems will exhibit potentially disastrous 鈥渆mergent behaviours鈥�, says David Cliff of Hewlett-Packard鈥檚 laboratory in Bristol, UK, who along with Seth Bullock at the University of Leeds wrote the report that prompted the government to address the issue.
Unpredictable behaviour
The task of debugging computer code grows exponentially with a program鈥檚 size, Cliff says, making full testing prohibitively expensive. 鈥淪ystems don鈥檛 always fail because the programmers are incompetent. It鈥檚 because they didn鈥檛 know about these unforeseen problems.鈥�
Computer systems are traditionally built by breaking up a problem into smaller parts, and assuming they will continue to work as planned when joined together. But as the number of modules increases, the ways in which they can interact becomes increasingly difficult to predict.
The 拢10 million the UK is to spend will be used to set up a national centre to study IT complexity, managed by the Engineering and Physical Sciences Research Council.
The centre will have its work cut out. The mathematics of complexity makes it impossible to explain the behaviour of a large distributed system simply in terms of the sum of its parts. Security threats like viruses and denial-of-service attacks can lead to unexpected emergent behaviours or even a crash.
Strange non-linear behaviours 鈥� those which produce a widespread effect from a relatively small change in a system鈥檚 operating condition 鈥� can result from single component failures, Cliff says. These behaviours can always be traced after an incident 鈥� but by then it is too late.