Legacy Systems and Business Process Reengineering
Business Rule Capture
By William Ulrich (Original text on http://www.systemtransformation.com)
L egacy systems are a rich untapped reserve of business rules that can be componentized and reused as part of the development process. Recreating the business rules contained in legacy systems would cost some companies more than their total fair market valuation.
Business process reengineering (BPR) allows management to realign organizational functions along more strategic lines. Companies examine processes now supporting the business and redesign those processes to reflect more efficient ways to achieve organizational goals. BPR is not an isolated phenomenon in today's highly automated environments. Information Systems (IS) organizations, due to the large installed base of legacy systems, play a key role in BPR efforts. Redesigning business processes that are tightly coupled with legacy systems implies that there will be a huge impact on those systems. Conversely, understanding current business functions requires analysis of these same systems. Fortunately, a rapidly emerging discipline supports analysis and migration of legacy systems to support BPR. It is called "Systems Redevelopment".
System transformation has several phases. These include enterprise and system-specific assessments, positioning of systems for ultimate transformation and the actual transformation stage itself. Some combination of these related disciplines are typically required to support changing business requirements.
Systems redevelopment has advantages over traditional analysis techniques. IT analysts,
isolated within functional areas, tend to miss the "big picture" view required to support
BPR analysis. Additionally, analysts may lack formal approaches for capturing and
depicting cross functional views of legacy systems. Systems redevelopment, however,
provides well defined analysis techniques and deliverables to support BPR. A second
advantage is that these analysis techniques provide the basis for an implementation plan
based on BPR project findings. Redevelopment techniques also leverage extraction / derivation
tools to streamline this process. Finally, formal redevelopment techniques can be
combined into various "scenarios" to support a wide array of BPR recommendations.
Many organizations have found that the IT department actually contains a company's functional expertise. But over time, that expertise has been lost. When company's make the decision to move to distributed systems or other technological environments, they need to determine what functions were currently being performed and what functions needed to be added. Business rule extraction is the way to determine what a company has before attempting to move forward."
While templates, packages and other reusable components streamline design efforts, business rules embedded in legacy systems still provide that "competitive edge". These rules are "locked up" in legacy systems and efforts to respecify them in today's high pressure, downsized environments is a costly, time consuming endeavor. Legacy rule capture and reuse has been described as the "missing link" in the systems transformation process.
Rule isolation and extraction is performed by tracing logic paths based on various selection criteria. This includes logic leading to the creation of a given output variable, logic linked to some type of conditional and logic associated with a given input transaction type. Analysts must review a rule after extraction in order to use it as is, extract again based on a different criteria or subset the extracted rule further. These techniques are somewhat tool dependent, but it is important to establish an initial extraction criteria regardless of the tool being applied.
Required rule extraction tool criteria minimally includes an ability to "slice" out a rule based on a specified selection criteria. Since business rules do not limit themselves to the confines of a source program, extraction tools must be able to analyze logic across program boundaries. Beyond that, a rule extraction tool should be able to bypass or highlight implementation dependent logic, store an extracted rule, further extract against a previously extracted rule, display a rule in varying formats to promote understandability and transform an extracted rule into a reusable format.
Certain tools can load a system into its knowledge base and transform it into
predicate logic. Rule analysis is then facilitated through cross system extraction
and simplification techniques. Rules may be displayed in decision vectors or as source
code. The real power of are that they allow IT professionals and non-technical analysts,
to examine extracted rules and verify what functions a system is actually performing.
Business rule capture is a key issue because most development projects do not have the luxury of starting from scratch.
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