Configuration decisions made. Reasoning not captured. Every future change becomes archaeology.
Implementation teams make hundreds of configuration decisions — workarounds chosen, standard functionality bypassed, trade-offs accepted. What gets documented is what was done, not why. The reasoning — the alternatives considered, the constraints that ruled them out, the criteria used — stays in the room with the people who were there, and leaves when they do.
Every change request reopens decisions nobody remembered making. Technical debt accumulates not in the code but in the absent reasoning behind it. Without a rationale field on significant configuration decisions, the implementation is perpetually at risk of contradicting itself — because no mechanism exists to know which decisions were load-bearing and why.
"Why is it built this way?" — a question that cannot be answered without finding the person who made the decision. That person may not be available. The reasoning was never written down. This is not a knowledge management problem. It is a structural gap that formed at the moment of decision.
These signals are observable during and after implementation. They indicate conditions under which the Rationale Gap has formed or is actively compounding.
A new request triggers a debate about whether a previous decision was right. Nobody can retrieve the reasoning that closed that debate the first time. The team re-litigates decisions they have already made, without the original context.
A team member encounters a configuration that is non-standard. There is no documentation of why standard functionality was bypassed. Finding the answer requires finding the person. That person may not be there.
Design documents, configuration logs, and runbooks capture outputs. They do not capture the reasoning behind them. A reader can verify what was done. They cannot evaluate whether it should be changed, or what changing it would break.
A person who joined after go-live cannot evaluate a configuration decision without seeking out someone who was present when it was made. The system requires oral history for basic operational reasoning.
The Rationale Gap is closed when any future team member — including one who was not present during the decision — can evaluate and explain a configuration choice without finding the original implementer. This is the test. Documentation that does not pass it is insufficient.
What was chosen, what alternatives were considered, what criteria ruled those alternatives out, and what constraint or priority made the chosen approach correct at the time.
The documentation makes clear which decisions are constraints — removing or changing them would break something — and which are preferences that can be revisited without cascading impact.
A person who joined after go-live can explain a workaround, evaluate a change request against it, and reason about the risk of modifying it — without a conversation with the person who built it.
Ask a team member who joined after go-live to explain why a specific workaround exists and what would break if it were removed. If the answer requires finding someone who was present at implementation, the Rationale Gap was not closed.
The Rationale Gap is distinct from adjacent problems that share surface symptoms. The intervention required differs by diagnosis.
Technical debt refers to implementation shortcuts — code or configuration that works now but will require rework later. The Rationale Gap can coexist with clean implementation. A workaround may be technically sound and rationale-free. The debt is not in what was built — it is in the absent reasoning that makes it impossible to evaluate, change, or explain.
Knowledge management implies information existed and was not stored properly. The Rationale Gap forms before any knowledge management system is involved — the reasoning was never externalised in the first place. The failure is not storage. It is capture.
Describing this as a documentation problem frames it as a discipline issue. It is a structural problem. The design of implementation processes does not include a rationale field. Teams document outputs because that is what the process asks for. No process element asks for reasoning. The gap is in the process, not the team.
These are publicly documented ERP implementation failures. Each illustrates how decisions made without captured reasoning created compounding failure when those decisions were revisited. Presented as diagnostic reference, not case studies.
Waste Management sued SAP claiming misrepresentation. When implementation problems surfaced, neither party could trace why the system had been configured the way it was. Design decisions had been made — but the reasoning behind them was absent. Change requests had nothing to anchor against. The dispute centred on intent that was never written down.
No captured rationale for configuration choices meant neither party could reconstruct the basis on which decisions were made. Every contested element required testimony rather than documentation.
Source: Computerworld ↗Marin County's SAP implementation stalled with the project roughly half complete. When auditors investigated, they found no documented rationale for staffing decisions, architectural choices, or configuration selections. When problems emerged, the project team could not explain why specific configurations were chosen — making it impossible to reason about what remediation would require or what risk it carried.
Without rationale behind decisions, there was no way to assess which were load-bearing and which were adjustable. Every change request became a full investigation from first principles.
Source: Computerworld ↗Revlon's SAP S/4HANA implementation at a North Carolina facility failed to record inventory correctly, generating $64 million in unfulfilled orders. Post-failure review found the implementation "lacked design and maintenance of effective controls." There was no documented rationale for control design decisions — no record of why certain safeguards were absent or what assumptions justified their omission.
Design decisions about inventory controls were made without captured reasoning. When the system failed, there was no documented logic explaining what was omitted or why — making accountability and remediation both harder to establish.
Source: Computer Weekly ↗