Monthly Archives: March 2007

Living with Constraints

Life, especially software development life, is never without constraints.

Time Constraints

  1. The software has to be released on a certain date, set well in advance. The only option is to plan based on the time budget.
  2. Given that I have this much time, what can I fit into this time?

Software Correctness (or Incorrectness) Constraints

  1. The software that you work with has flaws in it.
  2. How many flaws?
  3. Are the flaws of the software making it unusable? This is not any different than any other software you are trying to use. Windows has flaws in it, however once a problem is discovered, you are always trying to use the program in a way as to avoid that particular flaw.

Incomplete Knowledge Constraints (Requirements -> Problem -> Solution)

  1. The understanding of the requirements will evolve as you move through the project. More so, even the understanding of the folks who specify requirements will evolve.
  2. Your understanding of the problem evolves.
  3. Your understanding of the solution evolves.

Each constraint requires a different treatment. Each poses risk, therefore each needs to be dealt with, or the project will get into jeopardy. The questions to ask about each are:

Time Constraints

  1. What can I do in 2/20/200 hours?
  2. What % of my time should I spent on a given activity?
  3. What is the activity that only I can do?
  4. What is the activity that I can do that is visible?
  5. What are those activities that I can do to reduce other’s dependencies on me?
  6. What can I finish now to unblock to others?

Software Correctness

  1. Do I have proof in form of running code that this API I want to use works in the way I want to use it?
  2. Given that I found a problem with this API, is there a workaround that I can use?

Knowledge Constraints

  1. What are the requirements that are at risk to change because of real or perceived lack of clarity/definition/etc.?
  2. Is the problem formally described? If not, why not?
  3. Is the solution presented on paper proven to be correct (empirically or mathematically/logically)?
  4. Does the solution provide flexibility to cover for the risk of changing requirements?

People’s Skill and Knowledge Constraints

  1. What are the skills available in the team?
  2. What are the growth goals for the people on the team?

There is no constraint-free state. Our job as software engineers is to figure out a solution that can be completed within the constraints of time, people, money, etc. that we have. It is not an easy task, but that’s what makes it fun.