11 of
18 system satisfies those requirements. Throughout this section, every stated requirement should be
externally perceivable by users, operators, or other external systems. These requirements should
include at a minimum, a description of every input (stimulus) into the system, every output
(response) from the system, and all functions performed by the system in response to an input or in
support of an output. As this is often the largest and most important part of the SRS, the following
principles apply:
a)
Specific requirements should be stated in conformance with all the characteristics given
below:
a.
Correct
b.
Unambiguous
c.
Complete
d.
Consistent
e.
Ranked for importance and/or stability
f.
Verifiable
g.
Modifiable
h.
Traceable
b)
Specific requirements should be cross-referenced to earlier documents that relate.
c)
All requirements should be uniquely identifiable.
d)
Careful attention should be given to organizing the requirements to maximize readability.
Before examining specific ways of organizing the requirements it is helpful to understand the various
items that comprise requirements as described in Section 3.1 through Section 3.7
3.1 External interfaces Requirements This should be a detailed description of all inputs into and outputs from the software system. It
should complement the interface descriptions in Section 2 and should not repeat information there.
This subsection should also describe how the software operates inside various constraints. For
example, these constraints could include
a)
User interface requirements (section 3.1.1.)
b)
Hardware interface requirements (section 3.1.2)
c)
Software interface requirements (section 3.1.3)
d)
Communications interface requirements (section 3.1.4)
