2. Fundamental reasons why
establishing requirements for
complex systems will always be a
difficult technical and organisational
problem
Requirements engineering challenges, 2013
Slide 2
3. • Changing requirements
• Differing perspectives
• Lack of standardization
• People and politics
Requirements engineering challenges, 2013
Slide 3
4. Requirements change
• System requirements reflect the world outside
of the system.
• As this is constantly changing then the
requirements will inevitably also change
• It is often difficult to understand the
implications of changes for the requirements
as a whole
Requirements engineering challenges, 2013
Slide 4
5. Types of change
• Technology changes
– New technologies may have to be
incorporated into the system
• Organisational changes
– The business structure and organization
may change
Requirements engineering challenges, 2013
Slide 5
6. Environmental changes
• Market changes
– The market for a system may change
because of other systems introduced by
competitors or changed customer
expectations
• Economic changes
– The business may do better/worse than
Requirements engineering challenges, 2013
Slide 6
7. Political and legal changes
• External events lead to a change in
government policies or regulations
• In critical systems – these may lead to
requirements change
Requirements engineering challenges, 2013
Slide 7
8. Stakeholder perspectives
Technical perspective
Objects
Functions
Roles ...
Social perspective
Certification
perspective
User perspective
Interactions
Usability
Requirements engineering challenges, 2013
The problem and
the required system
Customer
perspective
Management perspective
Slide 8
9. Requirements conflicts
• Different perspectives are not consistent and
different stakeholders will want different
things from a system
• It is inevitable that some requirements will be
conflicting so that it is impossible to satisfy all
stakeholder requirements without
compromise
Requirements engineering challenges, 2013
Slide 9
10. Key stakeholders are busy
• Developing detailed requirements for
future systems often cannot be given a
high priority by the senior people who
will be affected by these requirements.
Requirements engineering challenges, 2013
Slide 10
11. • It is difficult to arrange meetings and
stakeholders do not have time to think
deeply about the system
• They therefore express their
requirements as vague, high-level
descriptions, which have to be
interpreted by engineers
Requirements engineering challenges, 2013
Slide 11
12. How good are the
requirements?
• There are no objective ways to
compare alternative sets of
requirements proposals to
decide which are ‘better’
Requirements engineering challenges, 2013
Slide 12
13. • The impact of a system on a business is
very hard to understand in advance so
therefore we cannot tell which might be
the ‘best’ system for any particular
business
Requirements engineering challenges, 2013
Slide 13
14. Quality improvement
• A common approach to quality improvement
is to develop an effective process then
standardize that process
• This means that all development then uses a
proven approach
• But this is very difficult for requirements
engineering
Requirements engineering challenges, 2013
Slide 14
15. Process and product variability
• The level of detail required in a requirements
specification differs greatly depending on the
type of product that is being developed
• Specifications for different types of system
may be expressed in completely different
ways
Requirements engineering challenges, 2013
Slide 15
16. • A railway signalling system is a very
detailed specification that can be
validated by authorities outside of the
organisation procuring the software
• A computer game specification is a
storyboard with pictures and examples
Requirements engineering challenges, 2013
Slide 16
17. Process variability
• Different companies use completely
different processes involving different
types of people to derive these
specifications
• Scope for process standardisation and
support is therefore limited
Requirements engineering challenges, 2013
Slide 17
18. Politics and people
• Many system requirements are
influenced by the politics in an
organisation.
• Decisions on requirements are not
made on a rational basis but are made
because of the personal goals of
stakeholders
Requirements engineering challenges, 2013
Slide 18
19. • New systems are often introduced to give
central management in an organization more
control and to ensure that all parts of the
organization work in the same way
• But this may be resisted by stakeholders who
use existing systems that are better suited to
their ways of working
Requirements engineering challenges, 2013
Slide 19
20. • Requirements engineers may not
understand the politics and, even when
they do, they may not be able to
challenge the ‘political’ requirements
Requirements engineering challenges, 2013
Slide 20
21. • People providing requirements for a system
may not be convinced that the system is
necessary or may feel that other systems
should have a higher priority.
• They may actively or passively refuse to
cooperate in the requirements engineering
process
Requirements engineering challenges, 2013
Slide 21
22. Summary
• Requirements engineering is an inherently
difficult process
• Issues that contribute to this difficulty are
– Changing requirements
– Differing views of system stakeholders
– Product and process variablity
– The political nature of system requirements
Requirements engineering challenges, 2013
Slide 22
