ISO can be used by specified users to

9241-10  deals  with 
software  aspects  and 
describes  seven  general 
ergonomic principles,  which  are 
independent  of  any 
specific  dialogue  technique; 
i.e.  they  are presented 
without  reference  to 
situations  of use,  applications, 
environments  or  technology. The following  table 
gives an  overview of the  seven principles  of ISO 
9241  and its  corresponding 

The seven principles of  ISO  9241/10 
and  corresponding descriptions.

We Will Write a Custom Essay Specifically
For You For Only $13.90/page!

order now



suitability for the 

A  dialogue  is 
suitable  for  a 
task  to  the extent 
that  it  supports 
the  user  in 
the effective  and  efficient 
completion  of the  task.


A  dialogue  is 
self-descriptive to  the  extent 
that  each  dialogue 
step  is  immediately 
comprehensible  through  feedback from  the 
system,  or  is 
explained  to  the user 
when  requesting  the 
relevant  information.


A  dialogue  is 
controllable  to  the 
extent that  the  user 
is  able  to 
maintain  direction  over the 
whole  course  of the 
interaction  until  the 
point  at  which 
the  goal has been  met.

conformity  with
user  expectations

A  dialogue  conforms 
with  user  expectations  to 
the  extent  that 
it  corresponds to  the 
user’s  task  knowledge, 
education,  experience,  and 
to  commonly  accepted conventions.

error tolerance

A  dialogue  is 
error  tolerant  to 
the  extent,  if 
despite  evident  errors 
in  input, the  intended 
result  may  be 
achieved with  either  no 
or  minimal  corrective action  having 
to be taken.

Suitability for

A  dialogue  is 
suitable  for  individualization  to 
the  extent  that 
the  dialogue system  is 
constructed  to  allow 
for modification  to  the 
user’s  individual needs  and 
skills  for a  given task.

 suitability for

A  dialogue  is 
suitable  for  learning 
to the  extent  that 
it  provides  support 
and guidance  to  the 
user  during  the 
learning  phases.



What is usability?

In the English 
language,  usability is  typically defined
as the “capability of being used”, implicitly the capability of an
entity to be used. From this perspective, usability  could be designed into the product, and
evaluated by assessing consistency with these 
design guidelines, or by heuristic evaluation.  This was the perspective taken in ISO 9126:1992:
“Software engineering—Product quality”, which defined usability as
“a set of attributes of software which bear on the effort needed for use
and on the individual assessment of such use by a stated or implied set of

The approach taken to usability in ISO 9241-11 (1998) was
similar, defining usability as: “The extent to which a product can be used
by specified users to achieve specified goals with effectiveness, efficiency
and satisfaction in a specified context of use.” This approach has the
benefit that it directly relates to user and business requirements:
effectiveness means success in achieving goals, efficiency means not wasting
time and satisfaction means willingness to use the system.

ISO 9241-11:1998 explains that in order to specify or measure
usability it is necessary to identify the goals and to decompose effectiveness,
efficiency and satisfaction and the components of the context of use into
sub-components with measurable and verifiable attributes.  The standard identifies the benefits of this

• The framework can be used to identify the usability
measures and the components of the context of use to be taken into account when
specifying, designing or evaluating the usability of a product.

• The performance (effectiveness and efficiency) and
satisfaction of the users can be used to measure the extent to which a product
is usable in a particular context.

• Measures of the performance and satisfaction of the users
can provide a basis for the comparison of the relative usability of products
with different technical characteristics which are used in the same context

• The level of usability needed  for a product can be defined, documented and
verified (e.g. as part of a quality plan).


It is important to understand the user’s experience:

In much early work in industry, usability was operationalized primarily in
terms of the user’s performance (effectiveness and efficiency), which was
regarded as the prime issue given the many problems that were experienced by
users of commercial systems.  But as use
of complex consumer products and of the World Wide Web became widespread, there
was an increasing awareness of the importance of the user’s subjective
reactions and emotional experience. This has led some authors to regard
usability as being restricted to “ease-of-use”, and relegate it to
the role of a “hygiene factor”, e.g. usability “…is a
thermometer that sets the ‘hygiene’ level of a product.

ISO 9241-210:2010 “Human-centred design for interactive systems”
defines  user experience as a
“person’s perceptions and responses resulting from the use and/or
anticipated use of a product, system or service”.  User experience focuses on the experience of
an individual in contrast with the view of effectiveness, efficiency and
satisfaction as representing the collective responses of a group of users.




ISO 9241:11


Systems, products, services and environments ISO 9241-11 currently applies
to the usability of “products”. In line with changes in standards
such as ISO 9241-210 this has been extended in the new draft to “products,
systems and services”, as the concept of usability applies equally well to
all these categories.  The new draft also
explains that although environments are considered as part of the context of
use, user interactions with a specific environment or component of the  environment can be considered in terms of the
usability of an environment  (e.g. the
smoothness of a path used by a wheelchair).


The current standard only mentions goals that achieve well-defined
outputs.  In reality, people may have
other reasons for interacting with a product, system or service, so the new
draft takes account of a much wider range of goals that include aspects of user

a)  output related outcome(s) that could either
be assigned (in an organizational context) and/or personally chosen;

b)  personal outcomes such as entertainment or
personal development;

c)  usability outcomes in terms of levels of
specific (sub)dimensions of usability, such as the desired level of accuracy;

d)  other outcomes (e.g. related to safety,
security or privacy) to be satisfied in the course of achieving output-related
or personal outcomes.


The effectiveness with which a goal is achieved was previously defined in
terms of accuracy and completeness. Appropriateness has been added as an
additional consideration that can include: a) the form and needed degree of
precision of the output (e.g. is information displayed appropriately on a web
page?) and b) avoidance of errors and minimization of the risk of any
unacceptable consequences that could arise from lack of accuracy and
completeness.  Adding appropriateness to
the other components of effectiveness goes some way towards taking account of
both the potential positive outcomes (accuracy and completeness) and the risk
of negative outcomes.


Efficiency was previously defined as the ratio of effectiveness divided by
the resources consumed. While this is scientifically correct as a productivity
measure, it is only meaningful for continuous output, which is not a common
situation. So, efficiency has been redefined in the revised standard as the
resources (time, human effort, costs and material resources) that are expended
when achieving a specific goal(e.g. the time to complete a specific task).


In the current ISO 9241-11, satisfaction is defined as “freedom from
discomfort, and positive attitudes towards the use of the product”. The
new draft  identifies  a much 
wider range of personal responses, including those  that have been highlighted in research on
user experience: “the extent to which attitudes related to the use of a
system, product or service and the emotional and physiological effects arising
from use are positive or negative”.

Avoidance of negative outcomes:

In the existing ISO 9241-11 effectiveness focuses on the accuracy and
completeness with which goals are achieved. But an unintended outcome can have
significant undesirable negative consequences for the individual or the
organization (such as inconvenience, wasted time, or financial loss