A Productive Response to Legacy Systems

Requirements change. The requirements of a legacy information system change, often

in unanticipated ways, and at a more rapid pace than the rate at which the information

system itself can be evolved to support them. The capabilities of a legacy system

progressively fall further and further behind their evolving requirements, in a degrading

process termed petrification. As systems petrify, they deliver diminishing business

value, hamper business effectiveness, and drain organisational resources.

To address legacy systems, the first challenge is to understand how to shed their

resistance to tracking requirements change. The second challenge is to ensure that a

newly adaptable system never again petrifies into a change resistant legacy system. This

thesis addresses both challenges.

The approach outlined herein is underpinned by an agile migration process - termed

Productive Migration - that homes in upon the specific causes of petrification within

each particular legacy system and provides guidance upon how to address them. That

guidance comes in part from a personalised catalogue of petrifying patterns, which

capture recurring themes underlying petrification. These steer us to the problems

actually present in a given legacy system, and lead us to suitable antidote productive

patterns via which we can deal with those problems one by one.

To prevent newly adaptable systems from again degrading into legacy systems, we

appeal to a follow-on process, termed Productive Evolution, which embraces and keeps

pace with change rather than resisting and falling behind it. Productive Evolution

teaches us to be vigilant against signs of system petrification and helps us to nip them in

the bud. The aim is to nurture systems that remain supportive of the business, that are

adaptable in step with ongoing requirements change, and that continue to retain their

value as significant business assets.