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20 March 2007

System life span: system definition

By Andrew Clifford

If you want to increase the life span of your systems, you have to clearly define your systems so that you can manage them effectively.

To increase system life span, you need to manage:

  • Ownership. IT requires responsible owners, to argue the case for resources and to make clear decisions.
  • Decoupling. Different areas of IT need to be kept separate from each other so that changes in one area do not disrupt other areas and shorten their life span.
  • Measurement. IT needs to be measured to understand what needs to be done to keep in step with the changing business and technical environment.

Without clear definition, you can not know what needs to be owned, what needs to be kept separate, and what needs to be measured. Without definition, IT is unmanageable.

Definition is not the same as design. Different design methods divide IT in different ways: by process, by data, by components, or as services. You can not manage using many different design views. You have to define one consistent structure over your IT so that it can be managed. (Though of course you should still have design views of our IT, and map these to the structures used for management.)

The best way to structure your IT so that it can be managed is to split it into systems, and to define each system clearly. To define a system clearly, give it a name and clearly define the boundaries of its functionality and its implementation.

Much of IT is already split into systems, and if these are clearly defined then they are a good basis for management. Where system definition is not clear, we need some guidelines.

  • Define systems by what they do, not how they are implemented. "Customer Order Processing" is a good system, "Mainframe" is bad.
  • Do not define systems by software version. "Oracle Financials 10" is not a good system because it will go out of date. "Finance Support" is a better system.
  • Do not name systems by the project used to implement them. Any system with newness its name (such as "new", "next generation", "genesis", "renewal" or "improved") sets expectations that it will be obsolete when it is no longer new.
  • Divide all your IT functionality into systems, not just your business applications. "Domain Name Service", "User Desktop" and "Email Service" are all systems.
  • Do not double count. Cross-system capabilities like "Oracle", "Performance Management" and "Storage" are not systems in their own right, but can be managed as characteristics of other systems.

Defining systems is not hard. It does not matter exactly where you draw the boundaries between systems, as long as they are clearly defined. If you really need to, you can adjust definitions later, though you do need to manage this carefully.

System definition is critical. It is often overlooked, or misunderstood because it is confused with design views. But a clear definition is vital for effective ownership, decoupling and measurement. With clear definition, you can start to manage the life span of your systems.

Next: Long-lived systems: ownership

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