Artifacts, such as
agile models and
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
Figure 1. The factors to determine JBGE.
Figure 2. How much effort should we invest in an artifact?
Let's consider the five strategies in order of preference:
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.
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.
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.
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.
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.