Thoughts About Scrum

Since now more than a decade, lightweight methodologies and processes have flourished under the umbrella of the Agile movement.

Despite the claimed success of Agile from daily practitioners, I haven’t seen many researches showing evidence that the Agile concepts really worked as expected; by this, I mean that Agile could still lead to reproducible success, but for other reasons that the one pushed by the various methodologies.

Here are a few open questions, especially about Scrum, for which I couldn’t find a decent answer. (For other related digression of mine, see real-world software development methodologies and What is a feature?)

Wasting time and unnecessary pressure

Scrum is organized around the notion of product backlog. One central notion in Scrum is that once started, the priorities of the current iteration won’t change; developers can focus and organize their work according to what’s been decided to go in the iteration, without being constantly disturbed by changes.

When a necessary change is detected, we tend to perceive it as highly prioritary: “We absolutely need this and that as soon as possible”. The existence of the product backlog and the frozen iteration improves this situation. Any story can be added anytime to the backlog. The priority of all stories will be reconsidered together when the next iteration starts. The process itself then promotes some relativity in the decisions that are taken, which is welcome as to lower the unnecessary pressure that is frequently generated.

Even though I heard this from a Scrum practitionner, I never found any evidence of this. It would however be possible to mine product backlogs to verify whether the priority of the stories tend to follow the scheme mentioned above: most of them are first entered with high priority, which then lowers over time. Only few stories are really prioritary, and the process helps their selection and identification (we could say the the signal-to-noise ratio is improved).

Delivering added-value

Another pillar of agile methodologies is to move away from technology engineering to product engineering. The team should focus on what brings most added-value – what make the software valuable – instead of what constitutes the software technically.

We see this tendency in several concepts:

  • Scrum has a user story, which is the expression of a valuable feature from the point of view of the end-user.
  • FDD has features, expressed in the form “<action> <result> <object>” (e.g. Calculate the total of a sale), which directly represents the value of the feature as perceived by the end-user.
  • TDD is less clear about this (and I’m not even sure if it’s considered as agile). Still, a test case can be perceived as the expression of a comprehensive feature.

While nice on paper, it’s not always easy to organize the development according to only added-value as perceived in the final product by the end-user.

For instance, the possible asymmetry between the complexity of the user story vs. the complexity in term of development effort, may impose a user story to be broken down into technology-related tasks.

The internal development tasks also escape the added-value scheme. A refactoring has no added-value from the customer point of view. How is then internal development effort managed in the context of agile methodologies?

I never found any clear positioning of agile practitioners regarding such problems. An analysis of existing backlog or issue trackers would be valuable to provide an explanation about how people manage this.

The case of bugs

Shipping a software product with no bug is an illusion. Bug reports,  bug triage and then bug fixing is part of the software development process.

Bugs and defects do however not fit very well with most agile methodologies. Should the user story or feature be reopened when a bug is reported? Should the bug be wrapped in a new story or features?

There isn’t lots of description of how the main development effort and the bug handling fit next to each other.
A study of how this happens in practice, both from point of view of the process but also from point of view of the tools (e.g. do most company still have an issue tracker to let customer report defects) would be interesting.

How agile are you?

The central point to agile, is well, to be agile. That is, to be able to adapt rapidely to changing requirements or situations. This stems from the fact that we can not anticipate everything, and that we can actually only anticipate very little when it comes to software development. And it’s a lot more rewarding and effective to improve the ability to face  changes than to desperately attempt to improve our ability to predict the future.

That said, there is no metrics for the “agility” of a team. It would however be interesting to define such a metrics (even if not a really tangible one) to be able to track progress in term of agility. Such a metric could be based on a mathematical model of how long user stories remain in the backlog.


Despite the wide acceptance of agile methodologies and the apparent success of these one, how they are really used in practice remains vague. It is especially hard to know how much the actual processes diverge in practice from the somehow theoretical vision of each methodology.  The methodologies do also not always address the whole spectrum of the software development lifecycle, in which case companies are probably introducing ad-hoc customizations and rules to cover their needs.

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