A passenger aircraft is composed of several millions of individual parts and requires thousands of persons to assemble. A four-lane highway bridge is another example of complexity. The ?rst version of Word for Windows, a word processor released by Microsoft in November 1989, required 55 person-years, resulted into 249,000 lines of source code, and was delivered 4 years late. Aircraft and highway bridges are usually delivered on time and below budget, whereas software is often not. Discuss what are, in your opinion, the differences between developing an aircraft, a bridge, and a word processor, which would cause this situation.

Question

What will be an ideal response?

Answer 1

This is an open question whose purpose is to have students realize that software systems are not the only complex systems out there. Answers should include two or more of the following points:
•To estimate the budget and schedule for a new bridge or aircraft, engineers use actual data from previous bridges and aircraft. Word for Windows was an innovative piece of software with few or no precedents.
• Many bridges and aircraft are simply re?nements of other existing artifacts. This reduces the proportion of the overall effort that is dedicated to design (which is the most dif?cult to estimate).
• Bridges and aircraft are often associated with severe ?nancial penalties when late or over budget.
• Bridges and aircraft have safety requirements associated with them. This leads to a conservative approach to development including the use of mature technologies and well de?ned processes.
• Bridges and aircraft are sometimes delivered late too.