The primary mission of an analyst or systems designer is to extract the physical requirements of the users and convert them to software. All software can trace its roots to a physical act or a physical requirement. A physical act can be defined as something that occurs in the interaction of people, that is, people create the root requirements of most systems, especially those in business. For example, when Mary tells us that she receives invoices from vendors and pays them thirty days later, she is explaining her physical activities during the process of receiving and paying invoices. When the analyst creates a technical specification which represents Mary's physical requirements, the specification is designed to allow for the translation of her physical needs into an automated environment. We know that software must operate within the confines of a computer, and such systems must function on the basis of logic.