Lauder, Anthony and Kent, Stuart
Legacy System Anti-Patterns and a Pattern-Oriented Migration Response.
In: Henderson, Philip J., ed.
Systems Engineering for Business Process Change.
(Full text available)
Mature information systems grow old disgracefully as successive waves of hacking result in accidental architectures which resist the reflection of on-going business process change. Such petrified systems are termed legacy systems. Legacy systems are simultaneously business assets and business liabilities. Their hard-won dependability and accurate reflection of tacit business knowledge prevents us from undertaking green-field development of replacement systems. Their resistance to the reflection of business process change prevents us from retaining them. Consequently, we are drawn in this paper to a controlled pattern-oriented legacy system migration strategy. Legacy systems exhibit six undesirable anti-patterns. A legacy system migration strategy must focus upon the controlled elimination of these anti-patterns by the step-wise application of six corresponding desirable patterns. Adherence to this migration strategy results in adaptive systems reflecting purposeful architectures open to the on-going reflection of business process change. Without such a strategy there is a very real danger that legacy system migration will occur all too literally. That is, the old legacy system will be migrated to a new legacy system albeit it one using the latest buzzword-compliant technology.
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