Legacy System Modernisation Work Breakdown Structure
This is a practical guide to building a work breakdown structure for a legacy system modernisation project — a deliverable-oriented decomposition of the whole scope into manageable work packages, adapted to the realities of modernising or replacing ageing core systems.
What a Work Breakdown Structure is
A work breakdown structure is a deliverable-oriented decomposition of the whole scope into manageable work packages. For the full concept and how it works in general, see Work Breakdown Structure. On a legacy system modernisation project it plays the same role, tuned to this kind of work.
Why it matters for a Legacy System Modernisation project
Legacy System Modernisation projects live or die on modernising or replacing ageing core systems. A well-built work breakdown structure gives the team a shared, explicit reference for exactly that — reducing ambiguity, aligning stakeholders, and making problems visible early enough to act. Skipping it, or doing it generically, is how legacy system modernisation projects drift into avoidable delay and cost.
What to include
- Top-level deliverables
- Sub-deliverables
- Work packages (8–80 hours)
- WBS numbering
- WBS dictionary entries
Legacy System Modernisation-specific considerations
Tailor the work breakdown structure to the risks that most often derail legacy system modernisation projects:
- Undocumented legacy behaviour
- Phased cutover risk
- Knowledge loss
Example
On a real legacy system modernisation project, the work breakdown structure would be shaped by modernising or replacing ageing core systems. In particular, it should explicitly account for the project’s biggest risks — undocumented legacy behaviour, phased cutover risk, knowledge loss — rather than treating them as afterthoughts.