Most software process models are intended to reduce risk.

Unlike the waterfall model, modern process models do not assume you will get everything right the first time. Revisiting and revising previous work is normal in these models.

One of the most straightforward ways to revise previous phases is to iterate the entire process.

• Build a version 0 in-house, and test it.
• Build a version 0.5 in-house, and use it.
• Build a version 0.75 in-house, and use it some more.
• Build a version 0.875 in-house, and get beta testers to use it.
• When version 1.0 is released, it won't be your first rodeo.

Release early, release often.