Legacy Systems and Business Process Reengineering
By William Ulrich (Original text on http://www.systemtransformation.com)
I n any BPR project, the as-is model should be used as a basis to redesign workflows. As processes are eliminated, updated, added, and re-sequenced, links to legacy system functions are maintained. The modeling approach used can be flexible, because the open transition model supports mapping of legacy functions to object, user interface, or other types of models. Upon completion of the new business model, work can begin on the retooling strategy. This requires an assessment of the existing architecture and target requirements which results in a detailed, retooling implementation plan.
The first step in the assessment requires management to identify feasible retooling hypotheses. This includes surround strategies, redevelopment, offshore options, internet options and / or package acquisition. Several basic issues drive which hypotheses are considered. An immediate requirement to address customer service consolidation may necessitate surround technology, such as graphical front-ends or data warehouse. An offshore rewrite could also serve as an interim strategy to stabilize a weak system. Additionally, selected off-the-shelf packages may meet retooling requirements. Finally, redeveloping impacted systems may be the ideal long-term solution to meet BPR requirements.
The analysis needed to finalize the retooling plan includes maintaining links between business models and detailed design models, further decomposition of legacy functions, and mapping legacy functions to detailed target models. The type and depth of analysis depends on the strategy being examined. Fore xample, requirements mapping to a package compares package models with target and legacy design models to determine reuse, deactivation, integration, and migration requirements.
Full-scale redevelopment, depending on the target architecture, requires detailed extraction and reuse of existing business rules. Extracted business rules must be mapped, at the applicable level of detail, to target design models. Augmentation of target models, and reuse of key business rules, can significantly streamline redevelopment cycles and shorten implementation windows. Many of the existing business rules can be reused under a target architecture. Organizations are spending a lot of money trying to recreate business rules when they don't have to.
These concepts challenge traditional BPR retooling strategies which include surrounding impacted systems or undertaking a complete rewrite. The first approach ignores the fact that underlying architectures remain segregated and convoluted. The second approach rarely accommodates legacy migration requirements and tends to exceed delivery windows and budget plans. Selecting a common sense approach, based on detailed analysis of target and existing architectures, yields the best results.
Several redevelopment options can be applied as a way to retool legacy architectures.
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