Expression of Requirements Definition/Meaning:
A statement of the requirements that some envisaged computer system (or program) is expected to meet. In order to define these requirements adequately,
it is normally necessary for the expression of requirements to address not just
the envisaged system but also the environment in which that system is to operate.
A good expression of requirements should be one of the earliest products of any
system-development project, and for a project of significant size it is of
crucial importance, not least because errors introduced at the requirements
stage tend to be the most expensive to correct. Since it is the first reasonably
complete description of any given system, its production presents several
significant problems. In particular it may be necessary to obtain information
from many individuals, none of whom have a full understanding of all aspects of
the envisaged system. There may therefore be a need to resolve several confused,
incomplete, and inconsistent views in order to produce a single coherent whole.
The expression of requirements is a primary vehicle for communication between
the procurers of a system and its developers, and must therefore be
understandable without specialist knowledge of computers or formal languages. A
natural language expression of requirements is normally inadequate and more
formal notations are usually adopted, often based on a graphical framework
within which natural language can be used.