Exogenous technical debt

Last updated on July 9th, 2021 at 04:58 pm

Exogenous technical debt is debt that arises from causes not directly related to the asset that bears the debt. Mastering understanding of exogenous technical debt is essential to controlling technical debt formation. Exogenous technical debt is particularly troublesome to those who work on the affected assets. They can’t control its formation, and they’re rarely responsible for creating it. But their internal customers and those who control resources often fail to understand this. Indeed, those who work on the affected assets often bear blame for the formation of exogenous technical debt even though they had no role in its formation, and could have done nothing to prevent its formation.

Exogenous technical debt and endogenous technical debt

Technical debt is exogenous when it’s brought about by an activity not directly related to the assets in which the debt appears. The word exogenous comes from the Greek exo– (outside) + –genous (related to producing). So exogenous technical debt is that portion of an asset’s debt that comes about from activities or decisions that don’t involve the asset directly.

Why we must track exogenous technical debt

Asbestos with muscovite.
Asbestos with muscovite. Asbestos is a family of minerals occurring naturally in fibrous form. The fibers are all known carcinogens. Until 1990, asbestos was a common ingredient of building materials, including insulation, plaster, and drywall joint compound. It’s now banned, but it’s present in existing homes and offices. The ban caused these structures to incur exogenous technical debt. Photo by Aramgutang courtesy Wikipedia.

Because so much technical debt arises indirectly, controlling its direct formation is insufficient to achieve control. To control technical debt formation, we must track which activities produce it. We must track both direct and indirect effects. Allocating technical debt retirement costs to the activities that brought that debt about is useful. It’s useful even if the allocation doesn’t affect budget authority for those activities. Knowledge about which past activities created technical debt, and how much, is helpful for long-term reduction in the rate of technical debt formation.

When we think of technical debt, we tend to think of activities that produce it relatively directly. We often imagine it as resulting solely from engineering activity, or from decisions not to undertake engineering activity. In either case the activity involved, whether undertaken or not, is activity directly involving the asset that carries—or which will be carrying—the technical debt. This kind of technical debt is endogenous technical debt. The word endogenous comes from the Greek endo– (within or inside) + –genous (related to producing). So endogenous technical debt is that portion of an asset’s debt that comes about from activities or decisions that directly involve the asset.

More about endogenous technical debt in future posts. For now, let’s look more closely at exogenous technical debt, and its policy implications.

Examples of exogenous technical debt

In “Spontaneous generation,” I examined one scenario in which technical debt formation occurs spontaneously—that is, in the absence of engineering activity. Specifically, I noted how the emergence of the HTML5 standard led to the formation of technical debt in some (if not all) existing Web sites. This happened because those sites didn’t exploit capabilities that had become available in HTML5. Moreover, some sites needed rehabilitation to remove emulations of the capabilities of the new standard. Those emulations needed to be replaced with use of facilities in the HTML5 standard. All of these artifacts—including those that existed, and those that didn’t—comprised technical debt. This scenario thus led to the formation of exogenous technical debt.

In a second example, AMUFC, A Made-Up Fictitious Corporation, incurs technical debt when the vendor that supplies the operating system (OS) for AMUFC’s desktop computers announces the date of the end of extended support for the version of the OS in use at AMUFC. Because the end of extended support brings an end to security updates, AMUFC must retire that debt by migrating to the next version of that vendor’s OS before extended support actually ends.

In both examples, the forces that lead to formation of exogenous technical debt are external to the enterprise and the enterprise’s assets. But what makes technical debt exogenous is that the forces that led to its formation are unrelated the engineering work being performed on the asset. This restriction is loose enough to also include technical debt that arises from any change or activity external to the asset, but within the enterprise.

Exogenous technical debt arising from actions within the enterprise

Exogenous technical debt can arise from activities or decisions that take place entirely within the enterprise.

For example, consider the line of mobile devices of AMUFC (A Made-Up Fictitious Corporation). Until this past year, AMUFC has been developing ever more capable devices. These efforts extended its line of offerings at the high end—the more expensive and capable members of the line. But this past quarter, AMUFC developed a low-end member of the line.

As often happens, price constraints for the low-cost device led to innovations. Those innovations could produce considerable savings in manufacturing costs if used all across the line. In effect, the designs of the previously developed higher-end models have incurred exogenous technical debt. The debt is exogenous because the activity that led to debt formation wasn’t performed on the assets that carry the debt. The debt is real, even though the activity that led to debt formation occurred within the enterprise. This kind of exogenous technical debt is asset-exogenous. Exogenous technical debt of the kind that results from activity beyond the enterprise is enterprise-exogenous.

Exogeneity versus endogeneity

For asset-exogenous technical debt, ambiguity between endogeneity and exogeneity can arise. The example above regarding the line of mobile devices produced by AMUFC provides an illustration.

For convenience, call the team that developed one of the high-end devices Team High. Call the team that developed the low-end device Team Low. From the perspective of Team High, the technical debt due to the innovations discovered by Team Low is exogenous. But from the perspective of the VP Mobile Devices, that same technical debt might be regarded as endogenous. The debt can be endogenous at VP level because it’s possible to regard the entire product line as a single asset, and that might actually be the preferred perspective of VP Mobile Devices.

This ambiguity can lead to some nasty toxic conflict. Team High and VP Mobile Devices might attack each other as they try to defend themselves proactively against claims that they are incurring technical debt. Avoiding this kind of conflict requires educating everyone as to the origins of technical debt.

Exogeneity and legacy technical debt

The technical debt portfolio of a given asset can contain a mix a technical debt that arose from various past incidents. In assessing the condition of the asset, it’s useful to distinguish this existing debt from debt that’s incurred as a consequence of any current activity or decisions. Call this pre-existing technical debt legacy technical debt.

The legacy technical debt an asset carries is technical debt associated with the asset, and which existed in any form before undertaking work on that asset. For example, consider planning a project to renovate the hallways and common areas of a high-rise apartment building. Suppose workers discover beneath the existing carpeting a layer of asbestos floor tile. Then Management might decide to remove the tile. In this context, we can regard the floor tile as legacy technical debt. It isn’t directly related to the objectives of the current renovation. But removing it will enhance the safety of future renovations. It will also enable certification of the building as asbestos-free, increase the property value, and reduce the cost of eventual demolition. In this situation asbestos removal is retirement of legacy technical debt. Accounting for it as part of the common-area renovation would be misleading.

Exogeneity is relevant when allocating resources for legacy technical debt retirement efforts. If the debt in question is enterprise-exogenous, we can justifiably budget the effort from enterprise-level accounts. For other cases, other resources become relevant, depending on what actions created the debt. For example, suppose that the technical debt arose from a change in enterprise standards. Then we can justifiably allocate retirement costs to the standard-setting initiative. If the exogenous technical debt arose from innovations in other members of the asset’s product line, we can can justifiably allocate those debt retirement costs to the product line.

Policy insights

Understanding the properties of exogenous technical debt can be a foundation for policy innovations that enhance enterprise agility.

Culture transformation

Widespread understanding of the distinction between exogenous and endogenous technical debt is helpful in controlling interpersonal conflict. For example, it can reduce blaming behavior that targets the engineering teams responsible for developing and maintaining technological assets.

Understanding asset-exogenous technical debt helps non-engineers understand how their actions and decisions can lead to technical debt formation. The concept clarifies the import of their actions even when there is no apparent direct connection between those actions or decisions and the assets in question.

Resource allocation

Data about the technical debt creation effects of enterprise activities is helpful in allocating technical debt retirement costs. For example, suppose that we know all the implications of reorganization, including its impact on internal data about the enterprise itself. Then we can charge data-related activity to the reorganization instead of to general accounts of the Information Technology function. This helps the enterprise understand the true costs of reorganization.

Similarly, data about enterprise-exogenous technical debt helps planners understand how to deploy resources to gather external intelligence about trends that can affect internal assets. Such data is also useful for setting levels of support and participation in industrial standards organizations or in lobbying government officials.

Last words

Knowing the formation history of exogenous technical debt provides useful guidance for those charged with allocating the costs of retiring technical debt or preventing its formation.

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