Why a Pure Waterfall Process is Usually Not Practical

• Don’t know up front everything wanted and needed

• Usually hard to visualize every detail in advance

• To gain confidence in an estimate, we need to design and actually implement parts, especially the riskiest ones, this may probably lead to modify requirements as a result

• We often need to execute intermediate builds

• Stakeholders need to gain confidence
• Designers and developers need confirmation they're building what’s needed and wanted

• Team members can't be idle while the requirements are being completed