MPrin in a development project

Last updated on July 7th, 2021 at 11:12 am

The "basket bridge" of the Los Angeles Metro system
The “basket bridge” of the Los Angeles Metro system. Constructed by the Metro Gold Line Foothill Extension Construction Authority, and opened in 2012, it carries the Los Angeles to Pasadena Metro Gold Line light rail across the eastbound lanes of the I-210 Freeway. The rail line provides transport service to a ridership that had been driving or using bus service. Although the bus and rail aren’t exact duplicates of each other, there is enough overlap that bus ridership dropped significantly after the rail line opened. That drop created a technical debt in the bus system. Retiring that debt requires reducing, rescheduling and re-routing bus service [Broverman 2017].

We usually regard the MPrin of new technical debt associated with a development project as the difference between the cost of implementing it sustainably and the cost of simply making it work. The effort saved by choosing the latter over the former is the initial MPrin of the technical debt.

For example, consider an enhancement project for an existing asset. After we achieve an operational capability, we might notice that we’ve duplicated some of the asset’s pre-existing functionality. The responsible debt-free approach has three stages. First, we eliminate the new and unnecessary duplicated capability. Next, we modify the asset to use the previously existing capability. Finally, we re-test the asset. The approach that generates new debt involves leaving the duplication in place.

Other generators of technical debt

In a closely related example, we might recognize that the duplicated functionality in the newly developed portion of the asset is superior to the pre-existing form elsewhere in the asset. We’d like to remove the pre-existing form and replace instances of that form with instances of the newly developed functionality. But that work is clearly outside the scope of the new development, and it must await budgetary authority before it can be undertaken. Consequently, it becomes technical debt for the larger asset.

As time passes, and the enterprise undertakes other development projects, the implementations of previous projects can accumulate additional technical debt. The more obvious mechanisms by which this occurs include defect discovery, customer requests for enhancements, the need to enhance cyberdefenses in response to new threats, or changes in law or regulation. Less obvious, but no less significant, are changes in markets, customer needs, and underlying technologies. All can contribute to technical debt formation

A final example

An example of a less obvious process might be insights gained in marketing one product (call it P1). Suppose those insights reveal an opportunity to introduce other related products—P2, P3, and P4—to form a suite. The latter products could employ some assets developed for P1, if the latter products had been constructed slightly differently. The changes required in P1 therefore constitute technical debt, because we would have been able to develop P2, P3, and P4 much more rapidly if we had recognized the opportunity earlier. The P1 changes then become technical debt. And if we pursue P2, P3, or P4 without first retiring that debt, the debt probably expands, because the subsequent products manifest it.

New product (or service) developments often generate these situations.


[Broverman 2017] Neal Broverman. “The Success of the Gold and Expo Lines Has Taken a Toll on Bus Ridership,” Los Angeles Magazine, March 30, 2017.

Available: here; Retrieved: November 21, 2017

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Examples of MPrin in four scenarios

Last updated on June 15th, 2021 at 01:57 pm

Some examples might help to clarify the differences between the principal of financial debts and the MPrin of a technical debt. The examples to come in the next four posts illustrate the unique properties of MPrins of technical debts.

Technical debt can arise as a result of:
  • Changes internally within the enterprise
  • External environmental changes that directly affect existing assets
  • Changes in the competitive environment
  • Insights and changes in perception that lead to changes in objectives
  • Existing technical debt
  • Deferring decisions about almost anything

By contrast, we incur financial debt only as a result of decisions to incur financial debt.

The examples below illustrate some of these phenomena. For each one, the full post contains a more complete explanation.

Development projects

This example illustrates how technical debt can develop as a result of unanticipated insight regarding a marketing opportunity for a new product line. It shows how technical debt can arise independent of any decision made within the enterprise, and without any changes to assets of any kind. More: “MPrin in a development project

Platform component upgrades

We’ve already provided an example of technical debt arising from a platform upgrade. In this example, we show how deferring a platform upgrade creates new complications not present in the previous example, by illustrating how total MPrin can increase after the debt first forms. More: “MPrin in a platform component upgrade

Standards or regulatory changes

Changes in standards or regulations, whether internal, industry-wide, or governmental, can create technical debt. In some cases, the enterprise might not even be aware of the new debt. More: “MPrin when standards or regulations change

Missing or incompletely implemented capability

When a capability is incompletely implemented, it’s clear that the part left undone constitutes technical debt. What is less clear is what happens when the capability implementation is halted or rescinded. Trying to avoid new technical debt can actually be the cause of new technical debt, albeit of a different kind. More: “MPrin for missing or incomplete capability

Whether or not any similar scenarios have happened in your organization, these discussions are helpful for gaining insight into what kinds of technical debt policies can assist your organization in managing its technical debt. Let me know if you have experience with situations in which problems can be traced, even if only in part, to treating technical debt as if it were financial debt.

Unintended associations of the technical debt metaphor

Last updated on July 8th, 2021 at 10:00 am

Because the term technical debt is a metaphor, it causes us to think in ways that sometimes create barriers to managing technical debt responsibly. Like all metaphors, the technical debt metaphor carries with it unintended associations—attributes of the metaphor’s source that the listener or reader attributes to the metaphor’s target, even though the attributions aren’t intended by the metaphor’s author. For the technical debt metaphor, these unintended associations relate to the concepts of debtor, principal, and interest, and they can cause enterprise decision makers to arrive at erroneous decisions.

Because metaphors compel our minds to accept the identification between source and target in toto, they can cause us to make errors of thought. Those errors create risks for the enterprise as we attempt to manage technical debt. The risk arises because we begin to regard technical debt as a form of financial debt, when in reality it is not. This misidentification is an acceptable risk, if we understand the risk and if we manage it properly. Unfortunately, we rarely recognize that risk. And unrecognized risks usually remain unmitigated. A significant source of this risk is our inability to control which attributes of the metaphor’s source the reader or listener chooses to associate with the metaphor’s target. I call this phenomenon unintended association.

Interest and principal have unintended associations

University graduates celebrate commencement
University graduates celebrate commencement. Some, perhaps most, carry a burden of student loan debt in addition to their diplomas. Student loans, now familiar to many, act as a source for the technical debt metaphor. They are therefore also a source for its unintended associations.
Two sets of unintended associations that frequently arise in the context of the technical debt metaphor relate to interest and principal. In the world of finance, we understand these concepts well. Unfortunately, our understanding from finance doesn’t fit well with the details of the corresponding properties of technical debt.

For example, van Haaster [van Haaster 2015] writes: “Financial debt has two well understood dimensions: the amount owing and its cost to repay over time, consequently when you take on financial debt, the total cost of that debt over time is either known or can be calculated.” Such beliefs about financial debt have consequences for our thinking about technical debt, because van Haaster’s statement is inapplicable to technical debt, for two reasons. First, the cost to repay a technical debt might not be well known. Second, the interest charges on technical debt might not be known, might not even be knowable, and often cannot be calculated [Falessi 2014]. These are just two examples of differences between financial debt and technical debt. We’ll explore these differences in some detail in coming posts.

How technical debt can be seen as evidence of mismanagement

A most significant unintended association is related to the concept of debt itself. Consider, for example, the social status of debtors in society. For many, excessive financial debt evokes images of profligate spending, laziness, and moral decay. These associations can hinder technology leaders within organizations as they urgently advocate for resources for technical debt management.

Because of unintended association, some decision makers outside the technology-oriented elements of the enterprise might regard technical debt as evidence of mismanagement. They might tend to attribute the cause of technical debt to professional malpractice by technologists. They see supportive evidence in the technology managers’ uncertainty about the size of the debt or how they acquired it. To the extent that nontechnical decision makers adopt this attitude, they are unlikely to support enterprise policy changes. They’re even less likely to support additional resources for technical debt management.

But the problems of the technical debt metaphor can be even more significant. The classic work of Lakoff and Johnson [Lakoff 1980] offers an explanation in terms of a metaphor (of course). In this metaphor:
  • Ideas are objects
  • Linguistic expressions are containers for ideas
  • Communication is the process of sending the containers along a conduit to a recipient

Metaphors have a significant weakness

Metaphors do have a significant weakness. When the recipient receives the container, he or she opens the container and extracts the idea. Unfortunately, things aren’t so simple. Lakoff and Johnson observe that the recipient must interpret the container’s contents relative to a context. But the recipient’s choice of context determines how well the metaphor serves the sender’s purposes. A broad array of context choices gives recipients freedom to interpret the linguistic expressions. That freedom is what leads to what I’ve been calling unintended associations.

For example, even within the enterprise’s technology sectors, the technical debt metaphor can create communication problems between technologists and their managers. Technologists are uniformly averse to technical debt. It makes their work more expensive and annoying. It limits their ability to enhance the assets they work with. To management, by contrast, the term debt evokes the idea of financial debt, which is useful when employed responsibly. Non-technologist managers don’t personally experience the frustrations and annoyance technical debt often causes. They don’t experience the visceral revulsion technologists feel when dealing with technical debt. The technical debt metaphor therefore accounts somewhat for differences in perceptions of technical debt.

When making the case for technical debt retirement, technologists must provide estimates of the scale of the problem, and explain how it arose. Those who interpret the term technical debt against a background of financial experience are likely to find unsettling the technologists’ admissions of total or partial ignorance of what led to the problem. Just as unsettling are the technologists’ admitted difficulties in estimating precisely the cost of retiring the technical debt. Such questions have definite answers for financial debt. For technical debt, they don’t, even though the terms financial debt and technical debt share the word debt.

Last words

Debates have erupted in the engineering literature about the meaning of the term technical debt. Is incomplete work technical debt if there had not been a conscious decision to postpone it? Is work performed shoddily to meet a tight schedule technical debt? The real problem isn’t ambiguity in the term technical debt; rather, it is that the term is only a metaphor. With regard to the technical debt metaphor, the range of possible interpretations is somewhat wider than some would like. Nearly all metaphors are subject to such problems.

It is this problem—a problem of all metaphors—that accounts for much of the difficulty enterprises have when they try to control technical debt.

But let’s turn now to a closer examination of the two most important unintended associations—principal and interest. We begin with principal next time.


[Broverman 2017] Neal Broverman. “The Success of the Gold and Expo Lines Has Taken a Toll on Bus Ridership,” Los Angeles Magazine, March 30, 2017.

Available: here; Retrieved: November 21, 2017

Cited in:

[Falessi 2014] D. Falessi, Philippe Kruchten, Robert L. Nord, and Ipek Ozkaya. “Technical Debt at the Crossroads of Research and Practice: Report on the Fifth International Workshop on Managing Technical Debt,” ACM SIGSOFT Software Engineering Notes 39:2, 31-33, 2014.

Available: here; Retrieved: March 16, 2017

Cited in:

[Lakoff 1980] George Lakoff and Mark Johnson. Metaphors We Live By. Chicago: The University of Chicago Press, 1980.

The classic and fundamental study of metaphor. Order from Amazon

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[van Haaster 2015] Kelsey van Haaster. “Technical Debt: A Systems Perspective,” Better Projects blog, January 8, 2015.

Available: here; Retrieved: October 2, 2017

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