How Much Modeling Should You Do?

Artifacts, such as agile models and agile documents should be sufficient for the task at hand, and no more. Agilists refer to this as just barely good enough(JBGE). This begs the question "How much modeling should you do?" The quick answer is less than you likely think.

The article When is an Artifact Just Barely Good Enough (JBGE)? explores the idea that JBGE is context dependent, determined by qualitative factors overviewed in Figure 1. Because the factors are qualitative in nature, the amount of modeling that you require for a given situation will be determined by an experience-based, "gut feel" decision. This may not be the answer that you were hoping for, but it's the honest one. Figure 2 explores the implications of this, overviewing five potential strategies for determining when you've modeled sufficiently.

Figure 1. The factors to determine JBGE.

Just barely good enough (JBGE)

Figure 2. How much effort should we invest in an artifact?

Just barely good enough (JBGE)

Let's consider the five strategies in order of preference:

  1. Ideal. Ideally you want to invest just enough effort in modeling and know more. Any effort beyond producing a model that is JBGE is a waste, and anything less is an indication that you can add more value from additional modeling.
  2. Efficient. Because the determinants of JBGE are qualitative in nature, you are best advised to do less modeling than what you currently require. This is because you can always do additional modeling when and if needed in the future, assuming the "Less Effort" factors of Figure 1 hold true. This is the zone that experienced agilists will aim for, although this can be a bit risky because the less effort factors might not actually hold true in practice.
  3. Comfortable. With this strategy you do a bit more modeling than is required, often because of old modeling habits around "maybe we're going to need this" thinking. This strategy is a bit wasteful because you've put more effort into the model than required. This is the zone that people new to agile will aim for, often because they need to gain additional experience with this strategy before agreeing with the idea of putting in less effort than they traditionally would have.
  4. Insufficient. With this strategy you simply haven't invested sufficient effort in modeling. You know you're in this zone when there are several serious unknowns or when you don't have agreement around several issues. You want to invest more effort if you find yourself in this zone. By definition, this is the zone in which you start when first creating a new model. You may find yourself in this zone because you underestimated the time required to model something, for example you scheduled a two-hour modeling session with stakeholders but found you needed to schedule another session in the future to finish the work.
  5. Overbuilt. With this strategy you have invested far too much effort in modeling, or the situation has changed significantly since the last time you worked on this model. Overbuilding a model is very wasteful because you've put more effort into it than what was actually required. Overbuilding is also potentially very risky, and costly, because now you have more to maintain, more information that can potentially be out of date, and you've increased the burden for the consumers of the model to understand it.

In summary, the determinants of when you've done enough modeling are qualitative in nature. As a result this decision is made based on the experience of the people involved. In short: It depends.

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