Chapter 1 : Measuring Legacy Complexity and its Impact on Business
As they grow older, legacy systems become more complex with a negative impact on the business: decreased agility, decreased quality of Service, decreased ease of use, increased costs and increased risk due to loss of knowledge.
To simplify your System, define your Enterprise System scope and simplification rationale with offensive (reduce time-to-market, offer new Functions…) and defensive (replace old technology…) objectives. Choose between different execution strategies (mandatory, self-standing, opportunistic or Architecture renewal program).
To justify the need for simplification, measure complexity and measure how it impacts the business. Complexity comes from the Business System, Organization System and IT System.
- Business System complexity can be measured by the number of Business Entities, Business Processes and Business Functions and by volumes (data and Process instances).
- Organization System complexity can be measured by the ratio of Organization Processes over Business Processes, Activities over Processes and Organization Functions over Business Functions, and by the number of Actors.
- IT System complexity can be measured by the number of assets (hardware, software, middleware), number of interfaces, databases, tables, number of Operations and development technologies, and by system and static code analysis.
Complexity can be reduced by a good Architecture and Architecture level and quality should be measured as well, but there is no established framework for that. Nevertheless CEISAR proposes tracks of what could be an Architecture level evaluation: common Business Processes and Functions, Common Organization Functions, Common Software Services, Shared Block Cartography, Level of parameterized settings…