In 1998, NASA launched the Mars Climate Orbiter, a $300 billion-plus spacecraft that traveled 400 million miles to the red planet. Even with speeds exceeding 3 miles per second, the journey took almost 9.5 months. Upon reaching its destination, the spacecraft fired its rockets to ease into a Mars orbit. The radio transmission was disrupted as the craft spun behind the planet and was expected only to resume 21 minutes later as it reappeared on the other side. Only it didn’t. The spacecraft was never heard from again.
NASA investigators determined that a definitional problem doomed the craft. The engine burn was timed to slow the ship down and place it in a safe orbit 68 miles above the planet’s surface. However, the instructions for the burn were wrong, resulting in the craft attempting to orbit Mars at a disastrous altitude of only 35 miles. The problem: NASA’s spacecraft was programmed to use the metric system while the commercial contractor sent burn information to NASA using the English system (pound-seconds instead of Newton-seconds). The burn lasted too long; the probe attempted to lower an orbit and burned up in the Mars atmosphere.
This is a pretty dramatic case of the definitional problem. The engineers’ thinking was sound; their math was accurate, and their numbers were correct; the definition of those numbers (English versus metric) was misunderstood.
A contentious area fueled by definitional problems is downtime. Imagine a situation where IT takes email offline every Sunday at 2:00 a.m. for preventive maintenance. At 2:10 a.m., the VP of marketing tries to send an email to the head of Europe, only to get a message that the email is not available. Later that month, the VP of marketing was surprised to see an IT report saying there was no email downtime. Result: The VP resolves never to trust IT reports again.
Who is right? Was email down that month? It depends on what you mean by down. It believes that down means an unscheduled interruption in service, while the user acknowledges that down means the service is unavailable, regardless of cause. Both groups have well-formulated, complete, and appropriate definitions; both definitions are adequate, accurate, and acceptable. They disagree.
Of more consequence is user management being told by IT that the total cost of their new accounting system will be $1,000,000, only to find that IT did not include in its budget transition end-user documentation or training costs. Question: who is correct? Answer: both.
When multiple parties are right, or at least not wrong, then the basis of the disagreement is probably definitional. In the example above, IT believes that the development cost consists of the hardware, software, and staffing expenses to analyze, design, code, and test a system, but not implementation, user documentation, and user training charges, which are to be borne by the user organization. The user believes the check he wrote for developing the system was the entire cost of getting his new application up and running. He is unaware of any additional “hidden” costs.
