Metaphors and the term technical debt

Last updated on July 7th, 2021 at 10:37 am

Ward Cunningham, who coined the technical debt metaphor
Ward Cunningham, who coined the technical debt metaphor. Photo (cc) Carrigg Photography.

The technical debt metaphor is both powerful and perilous. Its power lies in its ability to communicate the concept that some technological assets regarded as operational might—and probably do—need further attention. The peril arises when we think of this metaphorical technical debt as if it were a financial debt.

Ward Cunningham coined the technical debt metaphor in the context of developing a software asset [Cunningham 1992] [Cunningham 2011]. He observed that when the development process leads to new learning, re-executing the development project—or parts of the project—could lead to better results. For this reason, among others, newly developed software assets can contain, embody, or depend upon artifacts that, in hindsight, the developers recognize they could now remove, or replace with more elegant, effective, or appropriate forms. Those new forms would then enhance maintainability, defensibility, and extensibility. To deploy the asset in pre-hindsight condition would entail an obligation to return to it to implement the improvements hindsight revealed. That obligation is Cunningham’s conception of the asset’s technical debt.

This phenomenon applies to more than newly developed software. It applies to all technological assets. And it applies to new development, maintenance, cyberdefense, and enhancement.

Why Cunningham used a metaphor

Cunningham knew that he was using a metaphor to describe his situation. That situation is common in technological development projects—both software and hardware. He probably chose the debt metaphor because his audience was financially sophisticated. He was exploiting their knowledge of financial instruments to convey a concept that, from his perspective, properly belongs in the software engineering body of knowledge. Such uses of metaphors aren’t unusual.

For example, the leverage concept, which originates in mechanics, captures the idea of mechanical advantage. You’re exploiting mechanical advantage when using a rigid bar, resting on a fulcrum, to move a heavy object. Suppose a lever is arranged so that A is the distance from the heavy weight to the fulcrum. And suppose that B is the distance from the fulcrum to the point of application of the force. Then one gains a force “multiplier” of B/A. This concept has been used in the world of finance, renamed financial leverage, to describe how borrowing can confer on the borrower a financial “force multiplier” by increasing the borrower’s total financial power. From there, the term leverage has spread into the general business vocabulary. Indeed, we can now say that, “Cunningham leveraged his boss’s understanding of financial instruments to convey a concept from software engineering.”

Metaphors are powerful—and dangerous

The danger of metaphors arises when we rely on the audience to apply their experience to interpret them. But since everyone’s experience is different, we cannot be certain how the audience might interpret the metaphor. And that’s where the trouble begins.

Before we explore the technical debt metaphor, we must investigate the structure of metaphors. This study will clarify how the technical debt metaphor has evolved and how it continues to evolve. Even more important, a study of metaphors helps us understand and anticipate the communication problems that arise from the technical debt metaphor. We’ll look at the structure of metaphors next time.


[Cunningham 1992] Ward Cunningham. “The WyCash Portfolio Management System.” Addendum to the Proceedings of OOPSLA 1992. ACM, 1992.

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[Cunningham 2011] Ward Cunningham. “Ward Explains Debt Metaphor” (video; here; ).

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