Software Requirements



  Software Requirements.pdf (Size: 120.4 KB / Downloads: 3)

Types of requirements


Written for customers
– User requirements
• Statements in natural language plus diagrams of the
services the system provides and its operational
constraints.
• Written as a contract between client and
contractor
– System requirements
• A structured document setting out detailed
descriptions of the system services.
• Written for developers
– Software specification
• A detailed software description which can serve as a
basis for a design or implementation.


Functional requirements

• Statements of services the system
should provide, how the system
should react to particular inputs
and how the system should behave
in particular situations.


Requirements imprecision

• Problems arise when requirements are
not precisely stated
• Ambiguous requirements may be
interpreted in different ways by
developers and users
• Consider the term ‘appropriate viewers’
– User intention - special purpose viewer for
each different document type
– Developer interpretation - Provide a text
viewer that shows the contents of the
document


What requirements are these?


• It shall be possible for all necessary
communication between the APSE and
the user to be expressed in the standard
Ada character set
• The system development process and
deliverable documents shall conform to
the process and deliverables defined in
XYZCo-SP-STAN-95
• The system shall not disclose any
personal information about customers
apart from their name and reference
number to the operators of the system


Non-functional requirements


Define system properties and constraints
e.g. reliability, response time and
storage requirements. Constraints are
I/O device capability, system
representations, etc.
• Process requirements may also be
specified mandating a particular system,
programming language or development
method
• Non-functional requirements may be
more critical than functional
requirements. If these are not met, the
system is useless