Understanding Requirements - Requirements Engineering and Management for Software Development Projects - page 15

The functionality to enable persons with disabilities to use the product as also the
functionality to ensure that intruder prevention come under this category.
2. Safety functionality—This functionality protects the user from causing injury
to the users. However, as computer usage especially from this stand point
cannot cause physical injury, it has to protect him from logical injuries
including financial losses. Examples for safety functionality include charging
the credit card but not booking a ticket in online transactions, computational
inaccuracies, performing wrong transaction (buying shares when we intended
to sell), and data loss due to accidental deletes.
3. Security functionality—While safety functionality is to protect the user from
the product, security is safety from external attacks. Protection from intruders,
malicious use of insiders, and data theft via the Internet and so on are
examples of security functionality.
4. Usability functionality—It was originally referred to as User-friendliness.
The objective of this functionality is to make the software usable intuitively
and with minimal reference to user manuals. Graphical user Interface (GUI)
has achieved much of this functionality but improvement is always possible.
5. Data Integrity Protection functionality—Now that computing shifted from
EDP (Electronic Data Processing) rooms to end users, this has become an
important functionality for any software product. End user can unintentionally
and innocently affect data integrity. They may enter numerals in name fields
and alphabets in numeric fields. In Human Resources (HR) applications, they
may enter a date of birth such that the age of the employee may either be
below legal employment age or above the retirement age. In hospital or hotel
management applications, they may enter check out date as prior to check in
date. Users can enter wrong data in a hoard of ways. It is essential that all
necessary actions must be taken to prevent entry of wrong data. So data
validation requirements become important aspect of ancillary functionality.
6. Response time functionality—Sometimes, especially in real time applica-
tions, response times form part of core functionality. In business applications
however, they form part of ancillary functionality. In web based applications,
response times are important as the user and the server may not be at one
location and if the application does not respond fast enough, the user may
abort the application or do something else. Normally these form part of
organizational development standards.
7. Memory constraints functionality—With software controlling every device
today, the constraint still remains. It is a thing of the past as far as computers
are concerned but devices like mobile phones, cars, washing machines and the
like, not to mention rockets and space shuttles, memory constraints remains.
In these cases, memory constraint has to be taken into consideration. These
requirements can be obtained from hardware manufacturers who supply the
hardware on which the software needs to function.
8. Software footprint constraint—When the software resides on a chip in small
handheld devices and in various machines, the final size of the package that
gets installed becomes very important. Now all the Computer Numerically