Functional Decomposition of Your Legacy Application

160 hours
Challenges exist when working with legacy software. One challenge is a loss of knowledge related to that legacy software and a lack of comprehensive understanding of all the functionality the software supports. This loss of knowledge becomes most apparent when efforts are initiated that involve rewriting or refactoring a legacy system. To fully understand the scope of a legacy product and help ensure that all functionality is replicated, members of the Product Ownership Practice can detail a product's functionality by conducting a functional decomposition.


Functional decomposition is a process that ultimately serves to break down more complex systems into their fundamental components to offer a more transparent view of those systems. This analysis is critical for reducing costs and expediting the build of new systems by avoiding and removing waste. Upon completing a functional decomposition, teams can identify areas of duplication, low-value components and features for potential rationalization.

Deliverables and artifacts

A functional decomposition generally has two outputs:  

  • A diagram illustrating the parts of a larger system.
  • A narrative describing the details of the system's functionality.

Who should attend? 

  • Product Owners
  • Subject Matter Experts
  • Stakeholders


  • Thorough understanding of the current system and processes.
  • Highlighting risks by identifying the complexities of the system.
  • More efficient improvement planning.
  • A simplistic view of the system that any stakeholder can understand.
  • Save time and money as you seek to innovate through process improvements.