Documentation helps system designers develop new systems in much the same way that blueprints help architects design buildings. For example, professional IT personnel commonly hold structured walkthroughs in which they review system documentation to ensure the integrity and completeness of their designs, and to identify design flaws. Well-written documentation, along with other systems-design methodologies, often plays a key role in reducing systems failures and decreasing the time spent correcting ‘‘emergency errors’’ in computer systems. Conversely, poorly-designed systems usually lead to critical mistakes and expensive write-offs