Page 1399 - (ISC)² CISSP Certified Information Systems Security Professional Official Study Guide

one or two paragraphs. If you were reading a detailed summary of the
project, you might expect to see the concept statement as an abstract

or introduction that enables an outsider to gain a top-level
understanding of the project in a short period of time.

It’s very helpful to refer to the concept statement at all phases of the
systems development process. Often, the intricate details of the
development process tend to obscure the overarching goal of the
project. Simply reading the concept statement periodically can assist

in refocusing a team of developers.

Functional Requirements Determination

Once all stakeholders have agreed on the concept statement, it’s time
for the development team to sit down and begin the functional
requirements process. In this phase, specific system functionalities are
listed, and developers begin to think about how the parts of the system
should interoperate to meet the functional requirements. The
deliverable from this phase of development is a functional

requirements document that lists the specific system requirements.
These requirements should be expressed in a form consumable by
software developers. The following are the three major characteristics
of a functional requirement:

Input(s) The data provided to a function

Behavior The business logic describing what actions the system
should take in response to different inputs

Output(s) The data provided from a function

As with the concept statement, it’s important to ensure that all

stakeholders agree on the functional requirements document before
work progresses to the next level. When it’s finally completed, the
document shouldn’t be simply placed on a shelf to gather dust—the
entire development team should constantly refer to this document
during all phases to ensure that the project is on track. In the final

stages of testing and evaluation, the project managers should use this
document as a checklist to ensure that all functional requirements are
met.