What are the most significant differences among structured, object-oriented, and agile methods? What do they have in common?

The most significant differences among structured, object-oriented, and agile methods are in their approach to software development. Structured methods focus on a step-by-step process, with an emphasis on planning and documentation. Object-oriented methods emphasize the creation of reusable software components and the organization of code into objects. Agile methods, on the other hand, are focused on iterative development, with a high degree of collaboration and flexibility.

Despite these differences, all three methods share a common goal of producing high-quality software that meets the needs of the end user. They also prioritize designing and testing software to ensure it is both efficient and effective.