<s>
In	O
software	B-General_Concept
and	O
systems	O
engineering	O
,	O
the	O
phrase	O
use	B-Architecture
case	I-Architecture
is	O
a	O
polyseme	O
with	O
two	O
senses	O
:	O
</s>
<s>
A	O
usage	O
scenario	O
for	O
a	O
piece	O
of	O
software	B-General_Concept
;	O
often	O
used	O
in	O
the	O
plural	O
to	O
suggest	O
situations	O
where	O
a	O
piece	O
of	O
software	B-General_Concept
may	O
be	O
useful	O
.	O
</s>
<s>
A	O
use	B-Architecture
case	I-Architecture
is	O
a	O
list	O
of	O
actions	O
or	O
event	O
steps	O
typically	O
defining	O
the	O
interactions	O
between	O
a	O
role	O
(	O
known	O
in	O
the	O
Unified	B-Language
Modeling	I-Language
Language	I-Language
(	O
UML	B-Language
)	O
as	O
an	O
actor	B-Language
)	O
and	O
a	O
system	O
to	O
achieve	O
a	O
goal	O
.	O
</s>
<s>
The	O
actor	B-Language
can	O
be	O
a	O
human	O
or	O
another	O
external	O
system	O
.	O
</s>
<s>
In	O
systems	O
engineering	O
,	O
use	B-Architecture
cases	I-Architecture
are	O
used	O
at	O
a	O
higher	O
level	O
than	O
within	O
software	B-General_Concept
engineering	I-General_Concept
,	O
often	O
representing	O
missions	O
or	O
stakeholder	O
goals	O
.	O
</s>
<s>
The	O
detailed	O
requirements	O
may	O
then	O
be	O
captured	O
in	O
the	O
Systems	B-Language
Modeling	I-Language
Language	I-Language
(	O
SysML	B-Language
)	O
or	O
as	O
contractual	O
statements	O
.	O
</s>
<s>
In	O
1987	O
,	O
Ivar	O
Jacobson	O
presented	O
the	O
first	O
article	O
on	O
use	B-Architecture
cases	I-Architecture
at	O
the	O
OOPSLA'87	O
conference	O
.	O
</s>
<s>
He	O
described	O
how	O
this	O
technique	O
was	O
used	O
at	O
Ericsson	O
to	O
capture	O
and	O
specify	O
requirements	O
of	O
a	O
system	O
using	O
textual	O
,	O
structural	O
,	O
and	O
visual	B-Language
modeling	I-Language
techniques	O
to	O
drive	O
object-oriented	B-Application
analysis	I-Application
and	I-Application
design	I-Application
.	O
</s>
<s>
Originally	O
he	O
had	O
used	O
the	O
terms	O
usage	O
scenarios	O
and	O
usage	O
case	O
–	O
the	O
latter	O
a	O
direct	O
translation	O
of	O
his	O
Swedish	O
term	O
användningsfall	O
–	O
but	O
found	O
that	O
neither	O
of	O
these	O
terms	O
sounded	O
natural	O
in	O
English	O
,	O
and	O
eventually	O
he	O
settled	O
on	O
use	B-Architecture
case	I-Architecture
.	O
</s>
<s>
In	O
1992	O
he	O
co-authored	O
the	O
book	O
Object-Oriented	B-Language
Software	I-Language
Engineering	I-Language
-	O
A	O
Use	B-Architecture
Case	I-Architecture
Driven	O
Approach	O
,	O
which	O
laid	O
the	O
foundation	O
of	O
the	O
OOSE	B-Language
system	O
engineering	O
method	O
and	O
helped	O
to	O
popularize	O
use	B-Architecture
cases	I-Architecture
for	O
capturing	O
functional	O
requirements	O
,	O
especially	O
in	O
software	B-General_Concept
development	O
.	O
</s>
<s>
In	O
1994	O
he	O
published	O
a	O
book	O
about	O
use	B-Architecture
cases	I-Architecture
and	O
object-oriented	B-Language
techniques	O
applied	O
to	O
business	O
models	O
and	O
business	O
process	O
reengineering	O
.	O
</s>
<s>
At	O
the	O
same	O
time	O
,	O
Grady	O
Booch	O
and	O
James	O
Rumbaugh	O
worked	O
at	O
unifying	O
their	O
object-oriented	B-Application
analysis	I-Application
and	I-Application
design	I-Application
methods	O
,	O
the	O
Booch	O
method	O
and	O
Object	B-Application
Modeling	I-Application
Technique	I-Application
(	O
OMT	O
)	O
respectively	O
.	O
</s>
<s>
In	O
1995	O
Ivar	O
Jacobson	O
joined	O
them	O
and	O
together	O
they	O
created	O
the	O
Unified	B-Language
Modelling	I-Language
Language	I-Language
(	O
UML	B-Language
)	O
,	O
which	O
includes	O
use	B-Architecture
case	I-Architecture
modeling	O
.	O
</s>
<s>
UML	B-Language
was	O
standardized	O
by	O
the	O
Object	B-Architecture
Management	I-Architecture
Group	I-Architecture
(	O
OMG	O
)	O
in	O
1997	O
.	O
</s>
<s>
Jacobson	O
,	O
Booch	O
and	O
Rumbaugh	O
also	O
worked	O
on	O
a	O
refinement	O
of	O
the	O
Objectory	B-Application
software	B-General_Concept
development	O
process	O
.	O
</s>
<s>
The	O
resulting	O
Unified	O
Process	O
was	O
published	O
in	O
1999	O
and	O
promoted	O
a	O
use	B-Architecture
case	I-Architecture
driven	O
approach	O
.	O
</s>
<s>
Since	O
then	O
,	O
many	O
authors	O
have	O
contributed	O
to	O
the	O
development	O
of	O
the	O
technique	O
,	O
notably	O
:	O
Larry	O
Constantine	O
developed	O
in	O
1995	O
,	O
in	O
the	O
context	O
of	O
usage-centered	B-General_Concept
design	I-General_Concept
,	O
so	O
called	O
"	O
essential	O
use-cases	B-Architecture
"	O
that	O
aim	O
to	O
describe	O
user	O
intents	O
rather	O
than	O
sequences	O
of	O
actions	O
or	O
scenarios	O
which	O
might	O
constrain	O
or	O
bias	O
the	O
design	O
of	O
user	B-Application
interface	I-Application
;	O
Alistair	O
Cockburn	O
published	O
in	O
2000	O
a	O
goal-oriented	O
use	B-Architecture
case	I-Architecture
practice	O
based	O
on	O
text	O
narratives	O
and	O
tabular	O
specifications	O
;	O
Kurt	O
Bittner	O
and	O
Ian	O
Spence	O
developed	O
in	O
2002	O
advanced	O
practices	O
for	O
analyzing	O
functional	O
requirements	O
with	O
use	B-Architecture
cases	I-Architecture
;	O
Dean	O
Leffingwell	O
and	O
Don	O
Widrig	O
proposed	O
to	O
apply	O
use	B-Architecture
cases	I-Architecture
to	O
change	O
management	O
and	O
stakeholder	O
communication	O
activities	O
;	O
Gunnar	O
Overgaard	O
proposed	O
in	O
2004	O
to	O
extend	O
the	O
principles	O
of	O
design	O
patterns	O
to	O
use	B-Architecture
cases	I-Architecture
.	O
</s>
<s>
In	O
2011	O
,	O
Jacobson	O
published	O
with	O
Ian	O
Spence	O
and	O
Kurt	O
Bittner	O
the	O
ebook	O
Use	B-Architecture
Case	I-Architecture
2.0	O
to	O
adapt	O
the	O
technique	O
to	O
an	O
agile	O
context	O
,	O
enriching	O
it	O
with	O
incremental	O
use	B-Architecture
case	I-Architecture
"	O
slices	O
"	O
,	O
and	O
promoting	O
its	O
use	O
across	O
the	O
full	O
development	O
lifecycle	O
after	O
having	O
presented	O
the	O
renewed	O
approach	O
at	O
the	O
annual	O
IIBA	O
conference	O
.	O
</s>
<s>
Use	B-Architecture
cases	I-Architecture
are	O
a	O
technique	O
for	O
capturing	O
,	O
modeling	O
,	O
and	O
specifying	O
the	O
requirements	O
of	O
a	O
system	O
.	O
</s>
<s>
A	O
use	B-Architecture
case	I-Architecture
corresponds	O
to	O
a	O
set	O
of	O
behaviors	O
that	O
the	O
system	O
may	O
perform	O
in	O
interaction	O
with	O
its	O
actors	O
,	O
and	O
which	O
produces	O
an	O
observable	O
result	O
that	O
contributes	O
to	O
its	O
goals	O
.	O
</s>
<s>
In	O
the	O
requirement	O
analysis	O
,	O
at	O
their	O
identification	O
,	O
a	O
use	B-Architecture
case	I-Architecture
is	O
named	O
according	O
to	O
the	O
specific	O
user	O
goal	O
that	O
it	O
represents	O
for	O
its	O
primary	O
actor	B-Language
.	O
</s>
<s>
According	O
to	O
the	O
Software	B-General_Concept
Engineering	I-General_Concept
Body	O
of	O
Knowledge	O
(	O
SWEBOK	O
)	O
,	O
use	B-Architecture
cases	I-Architecture
belong	O
to	O
the	O
scenario-based	O
requirement	O
elicitation	O
techniques	O
,	O
as	O
well	O
as	O
the	O
model-based	B-Language
analysis	I-Language
,	O
techniques	O
.	O
</s>
<s>
But	O
the	O
use	B-Architecture
cases	I-Architecture
also	O
support	O
narrative-based	O
requirement	O
gathering	O
,	O
incremental	O
requirement	O
acquisition	O
,	O
system	O
documentation	O
,	O
and	O
acceptance	O
testing	O
.	O
</s>
<s>
There	O
are	O
different	O
kinds	O
of	O
use	B-Architecture
cases	I-Architecture
and	O
variations	O
in	O
the	O
technique	O
:	O
</s>
<s>
System	O
use	B-Architecture
cases	I-Architecture
specify	O
the	O
requirements	O
of	O
a	O
system	O
to	O
be	O
developed	O
.	O
</s>
<s>
Business	O
use	B-Architecture
cases	I-Architecture
focus	O
on	O
a	O
business	O
organization	O
instead	O
of	O
a	O
software	B-General_Concept
system	O
.	O
</s>
<s>
Essential	O
use	B-Architecture
cases	I-Architecture
,	O
also	O
called	O
abstract	O
use	B-Architecture
cases	I-Architecture
,	O
describe	O
the	O
potential	O
intents	O
of	O
the	O
actors	O
and	O
how	O
the	O
system	O
addresses	O
these	O
,	O
without	O
defining	O
any	O
sequence	O
or	O
describing	O
a	O
scenario	O
.	O
</s>
<s>
This	O
practice	O
was	O
developed	O
with	O
the	O
aim	O
of	O
supporting	O
the	O
user-centric	O
design	O
and	O
avoiding	O
to	O
induce	O
bias	O
about	O
the	O
user	B-Application
interface	I-Application
in	O
the	O
early	O
stage	O
of	O
the	O
system	O
specifications	O
.	O
</s>
<s>
Use	B-Architecture
Case	I-Architecture
2.0	O
to	O
adapt	O
the	O
technique	O
for	O
the	O
context	O
of	O
agile	O
development	O
methods	O
.	O
</s>
<s>
It	O
also	O
provides	O
use	B-Architecture
case	I-Architecture
"	O
slices	O
"	O
to	O
facilitate	O
incremental	O
elicitation	O
of	O
requirements	O
and	O
enable	O
incremental	O
implementation	O
.	O
</s>
<s>
The	O
scope	O
of	O
a	O
use	B-Architecture
case	I-Architecture
can	O
be	O
defined	O
by	O
a	O
subject	O
and	O
by	O
goals	O
:	O
</s>
<s>
Use	B-Architecture
cases	I-Architecture
are	O
known	O
to	O
be	O
applied	O
in	O
the	O
following	O
contexts	O
:	O
</s>
<s>
Object	B-Language
Oriented	I-Language
Software	B-General_Concept
Engineering	I-General_Concept
(	O
OOSE	B-Language
)	O
,	O
as	O
driving	O
element	O
;	O
</s>
<s>
Unified	B-Language
Modeling	I-Language
Language	I-Language
(	O
UML	B-Language
)	O
,	O
as	O
a	O
behavioral	O
modelling	O
instrument	O
;	O
</s>
<s>
Unified	O
Software	B-General_Concept
Development	O
Process	O
(	O
UP	O
)	O
and	O
its	O
fore-runner	O
,	O
the	O
IBM	B-Application
Rational	I-Application
Unified	I-Application
Process	I-Application
(	O
RUP	O
)	O
;	O
</s>
<s>
up-front	O
documentation	O
of	O
software	B-General_Concept
requirements	O
specification	O
(	O
SRS	O
)	O
,	O
as	O
an	O
alternative	O
structure	O
for	O
the	O
functional	O
requirements	O
;	O
</s>
<s>
There	O
are	O
many	O
ways	O
to	O
write	O
a	O
use	B-Architecture
case	I-Architecture
in	O
the	O
text	O
,	O
from	O
use	B-Architecture
case	I-Architecture
brief	O
,	O
casual	O
,	O
outline	O
,	O
to	O
fully	O
dressed	O
etc.	O
,	O
and	O
with	O
varied	O
templates	O
.	O
</s>
<s>
Writing	O
use	B-Architecture
cases	I-Architecture
in	O
templates	O
devised	O
by	O
various	O
vendors	O
or	O
experts	O
is	O
a	O
common	O
industry	O
practice	O
to	O
get	O
high-quality	O
functional	O
system	O
requirements	O
.	O
</s>
<s>
The	O
template	O
defined	O
by	O
Alistair	O
Cockburn	O
in	O
his	O
book	O
Writing	O
Effective	O
Use	B-Architecture
Cases	I-Architecture
has	O
been	O
one	O
of	O
the	O
most	O
widely	O
used	O
writing	O
styles	O
of	O
use	B-Architecture
cases	I-Architecture
.	O
</s>
<s>
Cockburn	O
suggests	O
annotating	O
each	O
use	B-Architecture
case	I-Architecture
with	O
a	O
symbol	O
to	O
show	O
the	O
"	O
Design	O
Scope	O
"	O
,	O
which	O
may	O
be	O
black-box	O
(	O
internal	O
detail	O
is	O
hidden	O
)	O
or	O
white	O
box	O
(	O
internal	O
detail	O
is	O
shown	O
)	O
.	O
</s>
<s>
Other	O
authors	O
sometimes	O
call	O
use	B-Architecture
cases	I-Architecture
at	O
the	O
Organization	O
level	O
"	O
Business	O
use	B-Architecture
cases	I-Architecture
"	O
.	O
</s>
<s>
Cockburn	O
suggests	O
annotating	O
each	O
use	B-Architecture
case	I-Architecture
with	O
a	O
symbol	O
to	O
show	O
the	O
"	O
Goal	O
Level	O
"	O
;	O
the	O
preferred	O
level	O
is	O
"	O
User-goal	O
"	O
(	O
or	O
colloquially	O
"	O
sea	O
level	O
"	O
)	O
.	O
</s>
<s>
Sometimes	O
in	O
text	O
writing	O
,	O
a	O
use	B-Architecture
case	I-Architecture
name	O
followed	O
by	O
an	O
alternative	O
text	O
symbol	O
(	O
!	O
</s>
<s>
Cockburn	O
describes	O
a	O
more	O
detailed	O
structure	O
for	O
a	O
use	B-Architecture
case	I-Architecture
but	O
permits	O
it	O
to	O
be	O
simplified	O
when	O
less	O
detail	O
is	O
needed	O
.	O
</s>
<s>
His	O
fully	O
dressed	O
use	B-Architecture
case	I-Architecture
template	O
lists	O
the	O
following	O
fields	O
:	O
</s>
<s>
In	O
addition	O
,	O
Cockburn	O
suggests	O
using	O
two	O
devices	O
to	O
indicate	O
the	O
nature	O
of	O
each	O
use	B-Architecture
case	I-Architecture
:	O
icons	O
for	O
design	O
scope	O
and	O
goal	O
level	O
.	O
</s>
<s>
Cockburn	O
's	O
approach	O
has	O
influenced	O
other	O
authors	O
;	O
for	O
example	O
,	O
Alexander	O
and	O
Beus-Dukic	O
generalize	O
Cockburn	O
's	O
"	O
Fully	O
dressed	O
use	B-Architecture
case	I-Architecture
"	O
template	O
from	O
software	B-General_Concept
to	O
systems	O
of	O
all	O
kinds	O
,	O
with	O
the	O
following	O
fields	O
differing	O
from	O
Cockburn	O
:	O
</s>
<s>
Cockburn	O
recognizes	O
that	O
projects	O
may	O
not	O
always	O
need	O
detailed	O
"	O
fully	O
dressed	O
"	O
use	B-Architecture
cases	I-Architecture
.	O
</s>
<s>
He	O
describes	O
a	O
Casual	O
use	B-Architecture
case	I-Architecture
with	O
the	O
fields	O
:	O
</s>
<s>
(	O
Story	O
)	O
:	O
the	O
body	O
of	O
the	O
use	B-Architecture
case	I-Architecture
is	O
simply	O
a	O
paragraph	O
or	O
two	O
of	O
text	O
,	O
informally	O
describing	O
what	O
happens	O
.	O
</s>
<s>
Martin	O
Fowler	O
states	O
"	O
There	O
is	O
no	O
standard	O
way	O
to	O
write	O
the	O
content	O
of	O
a	O
use	B-Architecture
case	I-Architecture
,	O
and	O
different	O
formats	O
work	O
well	O
in	O
different	O
cases.	O
"	O
</s>
<s>
A	O
use	B-Architecture
case	I-Architecture
defines	O
the	O
interactions	O
between	O
external	O
actors	O
and	O
the	O
system	O
under	O
consideration	O
to	O
accomplish	O
a	O
goal	O
.	O
</s>
<s>
Actors	O
must	O
be	O
able	O
to	O
make	O
decisions	O
,	O
but	O
need	O
not	O
be	O
human	O
:	O
"	O
An	O
actor	B-Language
might	O
be	O
a	O
person	O
,	O
a	O
company	O
or	O
organization	O
,	O
a	O
computer	O
program	O
,	O
or	O
a	O
computer	O
system	O
—	O
hardware	O
,	O
software	B-General_Concept
,	O
or	O
both.	O
"	O
</s>
<s>
Similarly	O
,	O
a	O
person	O
using	O
a	O
system	O
may	O
be	O
represented	O
as	O
a	O
different	O
actor	B-Language
because	O
of	O
playing	O
different	O
roles	O
.	O
</s>
<s>
This	O
tells	O
the	O
project	O
that	O
the	O
"	O
user	B-Application
interface	I-Application
and	O
security	O
clearances	O
"	O
should	O
be	O
designed	O
for	O
the	O
sales	O
rep	O
and	O
clerk	O
,	O
but	O
that	O
the	O
customer	O
and	O
marketing	O
department	O
are	O
the	O
roles	O
concerned	O
about	O
the	O
results	O
.	O
</s>
<s>
A	O
stakeholder	O
may	O
play	O
both	O
an	O
active	O
and	O
an	O
inactive	O
role	O
:	O
for	O
example	O
,	O
a	O
Consumer	O
is	O
both	O
a	O
"	O
mass-market	O
purchaser	O
"	O
(	O
not	O
interacting	O
with	O
the	O
system	O
)	O
and	O
a	O
User	O
(	O
an	O
actor	B-Language
,	O
actively	O
interacting	O
with	O
the	O
purchased	O
product	O
)	O
.	O
</s>
<s>
In	O
turn	O
,	O
a	O
User	O
is	O
both	O
a	O
"	O
normal	O
operator	O
"	O
(	O
an	O
actor	B-Language
using	O
the	O
system	O
for	O
its	O
intended	O
purpose	O
)	O
and	O
a	O
"	O
functional	O
beneficiary	O
"	O
(	O
a	O
stakeholder	O
who	O
benefits	O
from	O
the	O
use	O
of	O
the	O
system	O
)	O
.	O
</s>
<s>
Cockburn	O
advises	O
looking	O
for	O
actors	O
among	O
the	O
stakeholders	O
of	O
a	O
system	O
,	O
the	O
primary	O
and	O
supporting	O
(	O
secondary	O
)	O
actors	O
of	O
a	O
use	B-Architecture
case	I-Architecture
,	O
the	O
system	O
under	O
design	O
(	O
SuD	O
)	O
itself	O
,	O
and	O
finally	O
among	O
the	O
"	O
internal	O
actors	O
"	O
,	O
namely	O
the	O
components	O
of	O
the	O
system	O
under	O
design	O
.	O
</s>
<s>
In	O
the	O
same	O
way	O
that	O
a	O
use	B-Architecture
case	I-Architecture
describes	O
a	O
series	O
of	O
events	O
and	O
interactions	O
between	O
a	O
user	O
(	O
or	O
other	O
types	O
of	O
Actor	B-Language
)	O
and	O
a	O
system	O
,	O
in	O
order	O
to	O
produce	O
a	O
result	O
of	O
value	O
(	O
goal	O
)	O
,	O
a	O
business	O
use	B-Architecture
case	I-Architecture
describes	O
the	O
more	O
general	O
interaction	O
between	O
a	O
business	O
system	O
and	O
the	O
users/actors	O
of	O
that	O
system	O
to	O
produce	O
business	O
results	O
of	O
value	O
.	O
</s>
<s>
The	O
primary	O
difference	O
is	O
that	O
the	O
system	O
considered	O
in	O
a	O
business	O
use	B-Architecture
case	I-Architecture
model	O
may	O
contain	O
people	O
in	O
addition	O
to	O
technological	O
systems	O
.	O
</s>
<s>
In	O
the	O
example	O
of	O
a	O
restaurant	O
,	O
a	O
decision	O
must	O
be	O
made	O
whether	O
to	O
treat	O
each	O
person	O
as	O
an	O
actor	B-Language
(	O
thus	O
outside	O
the	O
system	O
)	O
or	O
a	O
business	O
worker	O
(	O
inside	O
the	O
system	O
)	O
.	O
</s>
<s>
If	O
a	O
waiter	O
is	O
considered	O
an	O
actor	B-Language
,	O
as	O
shown	O
in	O
the	O
example	O
below	O
,	O
then	O
the	O
restaurant	O
system	O
does	O
not	O
include	O
the	O
waiter	O
,	O
and	O
the	O
model	O
exposes	O
the	O
interaction	O
between	O
the	O
waiter	O
and	O
the	O
restaurant	O
.	O
</s>
<s>
An	O
alternative	O
would	O
be	O
to	O
consider	O
the	O
waiter	O
as	O
a	O
part	O
of	O
the	O
restaurant	O
system	O
(	O
a	O
business	O
worker	O
)	O
while	O
considering	O
the	O
client	O
to	O
be	O
outside	O
the	O
system	O
(	O
an	O
actor	B-Language
)	O
.	O
</s>
<s>
Use	B-Architecture
cases	I-Architecture
are	O
not	O
only	O
texts	O
but	O
also	O
diagrams	O
if	O
needed	O
.	O
</s>
<s>
In	O
the	O
Unified	B-Language
Modeling	I-Language
Language	I-Language
,	O
the	O
relationships	O
between	O
use	B-Architecture
cases	I-Architecture
and	O
actors	O
are	O
represented	O
in	O
use	B-Language
case	I-Language
diagrams	I-Language
originally	O
based	O
upon	O
Ivar	O
Jacobson	O
's	O
Objectory	B-Application
notation	O
.	O
</s>
<s>
SysML	B-Language
uses	O
the	O
same	O
notation	O
at	O
a	O
system	O
block	O
level	O
.	O
</s>
<s>
In	O
addition	O
,	O
other	O
behavioral	O
UML	B-Language
diagrams	I-Language
such	O
as	O
activity	O
diagrams	O
,	O
sequence	O
diagrams	O
,	O
communication	O
diagrams	O
,	O
and	O
state	B-Application
machine	I-Application
diagrams	I-Application
can	O
also	O
be	O
used	O
to	O
visualize	O
use	B-Architecture
cases	I-Architecture
accordingly	O
.	O
</s>
<s>
Specifically	O
,	O
a	O
System	O
Sequence	O
Diagram	O
(	O
SSD	O
)	O
is	O
a	O
sequence	O
diagram	O
often	O
used	O
to	O
show	O
the	O
interactions	O
between	O
the	O
external	O
actors	O
and	O
the	O
system	O
under	O
design	O
(	O
SuD	O
)	O
,	O
usually	O
for	O
visualizing	O
a	O
particular	O
scenario	O
of	O
a	O
use	B-Architecture
case	I-Architecture
.	O
</s>
<s>
Use	B-Architecture
case	I-Architecture
analysis	O
usually	O
starts	O
by	O
drawing	O
use	B-Language
case	I-Language
diagrams	I-Language
.	O
</s>
<s>
For	O
agile	O
development	O
,	O
a	O
requirement	O
model	O
of	O
many	O
UML	B-Language
diagrams	I-Language
depicting	O
use	B-Architecture
cases	I-Architecture
plus	O
some	O
textual	O
descriptions	O
,	O
notes	O
,	O
or	O
use	B-Architecture
case	I-Architecture
briefs	O
would	O
be	O
very	O
lightweight	O
and	O
just	O
enough	O
for	O
small	O
or	O
easy	O
project	O
use	O
.	O
</s>
<s>
As	O
good	O
complements	O
to	O
use	B-Architecture
case	I-Architecture
texts	O
,	O
the	O
visual	O
diagram	O
representations	O
of	O
use	B-Architecture
cases	I-Architecture
are	O
also	O
effective	O
facilitating	O
tools	O
for	O
the	O
better	O
understanding	O
,	O
communication	O
,	O
and	O
design	O
of	O
complex	O
system	O
behavioral	O
requirements	O
.	O
</s>
<s>
Below	O
is	O
a	O
sample	O
use	B-Architecture
case	I-Architecture
written	O
with	O
a	O
slightly	O
modified	O
version	O
of	O
the	O
Cockburn-style	O
template	O
.	O
</s>
<s>
Note	O
that	O
there	O
are	O
no	O
buttons	O
,	O
controls	O
,	O
forms	O
,	O
or	O
any	O
other	O
UI	O
elements	O
and	O
operations	O
in	O
the	O
basic	O
use	B-Architecture
case	I-Architecture
description	O
,	O
where	O
only	O
user	O
goals	O
,	O
subgoals	O
,	O
or	O
intentions	O
are	O
expressed	O
in	O
every	O
step	O
of	O
the	O
basic	O
flow	O
or	O
extensions	O
.	O
</s>
<s>
Alistair	O
Cockburn	O
lists	O
five	O
reasons	O
why	O
he	O
still	O
writes	O
use	B-Architecture
cases	I-Architecture
in	O
agile	O
development	O
.	O
</s>
<s>
The	O
main	O
success	O
scenario	O
of	O
each	O
use	B-Architecture
case	I-Architecture
provides	O
everyone	O
involved	O
with	O
an	O
agreement	O
as	O
to	O
what	O
the	O
system	O
will	O
basically	O
do	O
and	O
what	O
it	O
will	O
not	O
do	O
.	O
</s>
<s>
The	O
extension	O
conditions	O
of	O
each	O
use	B-Architecture
case	I-Architecture
provide	O
a	O
framework	O
for	O
investigating	O
all	O
the	O
little	O
,	O
niggling	O
things	O
that	O
somehow	O
take	O
up	O
80%	O
of	O
the	O
development	O
time	O
and	O
budget	O
.	O
</s>
<s>
The	O
use	B-Architecture
case	I-Architecture
extension	O
scenario	O
fragments	O
provide	O
answers	O
to	O
the	O
many	O
detailed	O
,	O
often	O
tricky	O
,	O
and	O
ignored	O
business	O
questions	O
:	O
"	O
What	O
are	O
we	O
supposed	O
to	O
do	O
in	O
this	O
case	O
?	O
"	O
</s>
<s>
The	O
full	O
use	B-Architecture
case	I-Architecture
set	O
shows	O
that	O
the	O
investigators	O
have	O
thought	O
through	O
every	O
user	O
's	O
needs	O
,	O
every	O
goal	O
they	O
have	O
with	O
respect	O
to	O
the	O
system	O
,	O
and	O
every	O
business	O
variant	O
involved	O
.	O
</s>
<s>
In	O
summary	O
,	O
specifying	O
system	O
requirements	O
in	O
use	B-Architecture
cases	I-Architecture
have	O
these	O
apparent	O
benefits	O
compared	O
with	O
traditional	O
or	O
other	O
approaches	O
:	O
</s>
<s>
Use	B-Architecture
cases	I-Architecture
constitute	O
a	O
powerful	O
,	O
user-centric	O
tool	O
for	O
the	O
software	B-General_Concept
requirements	O
specification	O
process	O
.	O
</s>
<s>
Use	B-Architecture
case	I-Architecture
modeling	O
typically	O
starts	O
from	O
identifying	O
key	O
stakeholder	O
roles	O
(	O
actors	O
)	O
interacting	O
with	O
the	O
system	O
,	O
and	O
their	O
goals	O
or	O
objectives	O
the	O
system	O
must	O
fulfill	O
(	O
an	O
outside	O
perspective	O
)	O
.	O
</s>
<s>
These	O
user	O
goals	O
then	O
become	O
the	O
ideal	O
candidates	O
for	O
the	O
names	O
or	O
titles	O
of	O
the	O
use	B-Architecture
cases	I-Architecture
which	O
represent	O
the	O
desired	O
functional	O
features	O
or	O
services	O
provided	O
by	O
the	O
system	O
.	O
</s>
<s>
Use	B-Architecture
case	I-Architecture
authoring	O
has	O
been	O
an	O
important	O
and	O
valuable	O
analysis	O
tool	O
in	O
the	O
domain	O
of	O
User-Centered	O
Design	O
(	O
UCD	O
)	O
for	O
years	O
.	O
</s>
<s>
Use	B-Architecture
cases	I-Architecture
are	O
often	O
written	O
in	O
natural	O
languages	O
with	O
structured	O
templates	O
.	O
</s>
<s>
This	O
narrative	O
textual	O
form	O
(	O
legible	O
requirement	O
stories	O
)	O
,	O
understandable	O
by	O
almost	O
everyone	O
,	O
and	O
complemented	O
by	O
visual	O
UML	B-Language
diagrams	I-Language
fosters	O
better	O
and	O
deeper	O
communications	O
among	O
all	O
stakeholders	O
,	O
including	O
customers	O
,	O
end-users	O
,	O
developers	O
,	O
testers	O
,	O
and	O
managers	O
.	O
</s>
<s>
One	O
of	O
the	O
most	O
powerful	O
things	O
about	O
use	B-Architecture
cases	I-Architecture
resides	O
in	O
the	O
formats	O
of	O
the	O
use	B-Architecture
case	I-Architecture
templates	O
,	O
especially	O
the	O
main	O
success	O
scenario	O
(	O
basic	O
flow	O
)	O
and	O
the	O
extension	O
scenario	O
fragments	O
(	O
extensions	O
,	O
exceptional	O
and	O
alternative	O
flows	O
)	O
.	O
</s>
<s>
Analyzing	O
a	O
use	B-Architecture
case	I-Architecture
step	O
by	O
step	O
from	O
preconditions	O
to	O
postconditions	O
,	O
exploring	O
and	O
investigating	O
every	O
action	O
step	O
of	O
the	O
use	B-Architecture
case	I-Architecture
flows	O
,	O
from	O
basic	O
to	O
extensions	O
,	O
to	O
identify	O
those	O
tricky	O
,	O
normally	O
hidden	O
and	O
ignored	O
,	O
seemingly	O
trivial	O
but	O
realistically	O
often	O
costly	O
requirements	O
(	O
as	O
Cockburn	O
mentioned	O
above	O
)	O
,	O
is	O
a	O
structured	O
and	O
beneficial	O
way	O
to	O
get	O
clear	O
,	O
stable	O
and	O
quality	O
requirements	O
systematically	O
.	O
</s>
<s>
Minimizing	O
and	O
optimizing	O
the	O
action	O
steps	O
of	O
a	O
use	B-Architecture
case	I-Architecture
to	O
achieve	O
the	O
user	O
goal	O
also	O
contribute	O
to	O
a	O
better	O
interaction	B-General_Concept
design	I-General_Concept
and	O
user	B-Application
experience	I-Application
of	O
the	O
system	O
.	O
</s>
<s>
With	O
content	O
based	O
upon	O
an	O
action	O
or	O
event	O
flow	O
structure	O
,	O
a	O
model	O
of	O
well-written	O
use	B-Architecture
cases	I-Architecture
also	O
serves	O
as	O
excellent	O
groundwork	O
and	O
valuable	O
guidelines	O
for	O
the	O
design	O
of	O
test	O
cases	O
and	O
user	O
manuals	O
of	O
the	O
system	O
or	O
product	O
,	O
which	O
is	O
an	O
effort-worthy	O
investment	O
up-front	O
.	O
</s>
<s>
There	O
are	O
obvious	O
connections	O
between	O
the	O
flow	O
paths	O
of	O
a	O
use	B-Architecture
case	I-Architecture
and	O
its	O
test	O
cases	O
.	O
</s>
<s>
Deriving	O
functional	O
test	O
cases	O
from	O
a	O
use	B-Architecture
case	I-Architecture
through	O
its	O
scenarios	O
(	O
running	O
instances	O
of	O
a	O
use	B-Architecture
case	I-Architecture
)	O
is	O
straightforward	O
.	O
</s>
<s>
Limitations	O
of	O
use	B-Architecture
cases	I-Architecture
include	O
:	O
</s>
<s>
Use	B-Architecture
cases	I-Architecture
are	O
not	O
well	O
suited	O
to	O
capturing	O
non-interaction-based	O
requirements	O
of	O
a	O
system	O
(	O
such	O
as	O
algorithm	O
or	O
mathematical	O
requirements	O
)	O
or	O
non-functional	O
requirements	O
(	O
such	O
as	O
platform	O
,	O
performance	O
,	O
timing	O
,	O
or	O
safety-critical	O
aspects	O
)	O
.	O
</s>
<s>
As	O
there	O
are	O
no	O
fully	O
standard	O
definitions	O
of	O
use	B-Architecture
cases	I-Architecture
,	O
each	O
project	O
must	O
form	O
its	O
own	O
interpretation	O
.	O
</s>
<s>
Use	B-Architecture
case	I-Architecture
developers	O
often	O
find	O
it	O
difficult	O
to	O
determine	O
the	O
level	O
of	O
user	B-Application
interface	I-Application
(	O
UI	O
)	O
dependency	O
to	O
incorporate	O
in	O
a	O
use	B-Architecture
case	I-Architecture
.	O
</s>
<s>
While	O
use	B-Architecture
case	I-Architecture
theory	O
suggests	O
that	O
UI	O
not	O
be	O
reflected	O
in	O
use	B-Architecture
cases	I-Architecture
,	O
it	O
can	O
be	O
awkward	O
to	O
abstract	O
out	O
this	O
aspect	O
of	O
design	O
,	O
as	O
it	O
makes	O
the	O
use	B-Architecture
cases	I-Architecture
difficult	O
to	O
visualize	O
.	O
</s>
<s>
In	O
software	B-General_Concept
engineering	I-General_Concept
,	O
this	O
difficulty	O
is	O
resolved	O
by	O
applying	O
requirements	O
traceability	O
,	O
for	O
example	O
with	O
a	O
traceability	O
matrix	O
.	O
</s>
<s>
Another	O
approach	O
to	O
associate	O
UI	O
elements	O
with	O
use	B-Architecture
cases	I-Architecture
is	O
to	O
attach	O
a	O
UI	O
design	O
to	O
each	O
step	O
in	O
the	O
use	B-Architecture
case	I-Architecture
.	O
</s>
<s>
This	O
is	O
called	O
a	O
use	B-Architecture
case	I-Architecture
storyboard	O
.	O
</s>
<s>
Use	B-Architecture
cases	I-Architecture
can	O
be	O
over-emphasized	O
.	O
</s>
<s>
Bertrand	O
Meyer	O
discusses	O
issues	O
such	O
as	O
driving	O
system	O
design	O
too	O
literally	O
from	O
use	B-Architecture
cases	I-Architecture
,	O
and	O
using	O
use	B-Architecture
cases	I-Architecture
to	O
the	O
exclusion	O
of	O
other	O
potentially	O
valuable	O
requirements	O
analysis	O
techniques	O
.	O
</s>
<s>
Use	B-Architecture
cases	I-Architecture
are	O
a	O
starting	O
point	O
for	O
test	O
design	O
,	O
but	O
since	O
each	O
test	O
needs	O
its	O
own	O
success	O
criteria	O
,	O
use	B-Architecture
cases	I-Architecture
may	O
need	O
to	O
be	O
modified	O
to	O
provide	O
separate	O
post-conditions	O
for	O
each	O
path	O
.	O
</s>
<s>
Though	O
use	B-Architecture
cases	I-Architecture
include	O
goals	O
and	O
contexts	O
,	O
whether	O
these	O
goals	O
and	O
motivations	O
behind	O
the	O
goals	O
(	O
stakeholders	O
 '	O
concerns	O
and	O
their	O
assessments	O
including	O
non-interaction	O
)	O
conflict	O
or	O
negatively/positively	O
affect	O
other	O
system	O
goals	O
are	O
subject	O
of	O
goal-oriented	O
requirement	O
modeling	O
techniques	O
(	O
such	O
as	O
BMM	O
,	O
I*	B-Language
,	O
KAOS	O
and	O
ArchiMate	B-Architecture
ARMOR	O
)	O
.	O
</s>
<s>
Common	O
misunderstandings	O
about	O
use	B-Architecture
cases	I-Architecture
are	O
:	O
</s>
<s>
User	O
stories	O
are	O
agile	O
;	O
use	B-Architecture
cases	I-Architecture
are	O
not	O
.	O
</s>
<s>
Those	O
items	O
can	O
be	O
expressed	O
as	O
user	O
stories	O
,	O
use	B-Architecture
cases	I-Architecture
,	O
or	O
any	O
other	O
requirements	O
approach	O
that	O
the	O
group	O
finds	O
useful	O
.	O
</s>
<s>
Use	B-Architecture
case	I-Architecture
techniques	O
have	O
evolved	O
to	O
take	O
Agile	O
approaches	O
into	O
account	O
by	O
using	O
use	B-Architecture
case	I-Architecture
slices	O
to	O
incrementally	O
enrich	O
a	O
use	B-Architecture
case	I-Architecture
.	O
</s>
<s>
Use	B-Architecture
cases	I-Architecture
are	O
mainly	O
diagrams	O
.	O
</s>
<s>
Craig	O
Larman	O
stresses	O
that	O
"	O
use	B-Architecture
cases	I-Architecture
are	O
not	O
diagrams	O
,	O
they	O
are	O
text	O
"	O
.	O
</s>
<s>
Use	B-Architecture
cases	I-Architecture
have	O
too	O
much	O
UI-related	O
content	O
.	O
</s>
<s>
Use	B-Architecture
cases	I-Architecture
will	O
often	O
contain	O
a	O
level	O
of	O
detail	O
(	O
i.e.	O
</s>
<s>
Each	O
step	O
of	O
a	O
well-written	O
use	B-Architecture
case	I-Architecture
should	O
present	O
actor	B-Language
goals	O
or	O
intentions	O
(	O
the	O
essence	O
of	O
functional	O
requirements	O
)	O
,	O
and	O
normally	O
it	O
should	O
not	O
contain	O
any	O
user	B-Application
interface	I-Application
details	O
,	O
e.g.	O
</s>
<s>
naming	O
of	O
labels	O
and	O
buttons	O
,	O
UI	O
operations	O
,	O
etc.	O
,	O
which	O
is	O
a	O
bad	O
practice	O
and	O
will	O
unnecessarily	O
complicate	O
the	O
use	B-Architecture
case	I-Architecture
writing	O
and	O
limit	O
its	O
implementation	O
.	O
</s>
<s>
As	O
for	O
capturing	O
requirements	O
for	O
a	O
new	O
system	O
from	O
scratch	O
,	O
use	B-Language
case	I-Language
diagrams	I-Language
plus	O
use	B-Architecture
case	I-Architecture
briefs	O
are	O
often	O
used	O
as	O
handy	O
and	O
valuable	O
tools	O
,	O
at	O
least	O
as	O
lightweight	O
as	O
user	O
stories	O
.	O
</s>
<s>
Writing	O
use	B-Architecture
cases	I-Architecture
for	O
large	O
systems	O
is	O
tedious	O
and	O
a	O
waste	O
of	O
time	O
.	O
</s>
<s>
The	O
format	O
of	O
the	O
use	B-Architecture
case	I-Architecture
makes	O
it	O
difficult	O
to	O
describe	O
a	O
large	O
system	O
(	O
e.g.	O
</s>
<s>
Spending	O
much	O
time	O
writing	O
tedious	O
use	B-Architecture
cases	I-Architecture
which	O
add	O
no	O
or	O
little	O
value	O
and	O
result	O
in	O
a	O
lot	O
of	O
rework	O
is	O
a	O
bad	O
smell	O
indicating	O
that	O
the	O
writers	O
are	O
not	O
well	O
skilled	O
and	O
have	O
little	O
knowledge	O
of	O
how	O
to	O
write	O
quality	O
use	B-Architecture
cases	I-Architecture
both	O
efficiently	O
and	O
effectively	O
.	O
</s>
<s>
Use	B-Architecture
cases	I-Architecture
should	O
be	O
authored	O
in	O
an	O
iterative	O
,	O
incremental	O
,	O
and	O
evolutionary	O
(	O
agile	O
)	O
way	O
.	O
</s>
<s>
Applying	O
use	B-Architecture
case	I-Architecture
templates	O
does	O
not	O
mean	O
that	O
all	O
the	O
fields	O
of	O
a	O
use	B-Architecture
case	I-Architecture
template	O
should	O
be	O
used	O
and	O
filled	O
out	O
comprehensively	O
from	O
up-front	O
or	O
during	O
a	O
special	O
dedicated	O
stage	O
,	O
i.e.	O
</s>
<s>
In	O
fact	O
,	O
the	O
use	B-Architecture
case	I-Architecture
formats	O
formulated	O
by	O
those	O
popular	O
template	O
styles	O
,	O
e.g.	O
</s>
<s>
the	O
RUP	O
's	O
and	O
the	O
Cockburn	O
's	O
(	O
also	O
adopted	O
by	O
the	B-Application
OUM	I-Application
method	I-Application
)	O
,	O
etc.	O
,	O
have	O
been	O
proved	O
in	O
practice	O
as	O
valuable	O
and	O
helpful	O
tools	O
for	O
capturing	O
,	O
analyzing	O
and	O
documenting	O
complex	O
requirements	O
of	O
large	O
systems	O
.	O
</s>
<s>
The	O
quality	O
of	O
a	O
good	O
use	B-Architecture
case	I-Architecture
documentation	O
(	O
model	O
)	O
should	O
not	O
be	O
judged	O
largely	O
or	O
only	O
by	O
its	O
size	O
.	O
</s>
<s>
It	O
is	O
possible	O
as	O
well	O
that	O
a	O
quality	O
and	O
comprehensive	O
use	B-Architecture
case	I-Architecture
model	O
of	O
a	O
large	O
system	O
may	O
finally	O
evolve	O
into	O
hundreds	O
of	O
pages	O
mainly	O
because	O
of	O
the	O
inherent	O
complexity	O
of	O
the	O
problem	O
in	O
hand	O
,	O
not	O
because	O
of	O
the	O
poor	O
writing	O
skills	O
of	O
its	O
authors	O
.	O
</s>
<s>
Text	O
editors	O
and/or	O
word	B-General_Concept
processors	I-General_Concept
with	O
template	O
support	O
are	O
often	O
used	O
to	O
write	O
use	B-Architecture
cases	I-Architecture
.	O
</s>
<s>
For	O
large	O
and	O
complex	O
system	O
requirements	O
,	O
dedicated	O
use	B-Architecture
case	I-Architecture
tools	O
are	O
helpful	O
.	O
</s>
<s>
Some	O
of	O
the	O
well-known	O
use	B-Architecture
case	I-Architecture
tools	O
include	O
:	O
</s>
<s>
Rational	O
Software	B-General_Concept
's	O
RequisitePro	O
-	O
one	O
of	O
the	O
early	O
,	O
well-known	O
use	B-Architecture
case	I-Architecture
and	O
requirement	O
management	O
tools	O
in	O
the	O
1990s	O
.	O
</s>
<s>
Wiki	B-Protocol
software	I-Protocol
-	O
good	O
tools	O
for	O
teams	O
to	O
author	O
and	O
manage	O
use	B-Architecture
cases	I-Architecture
collaboratively	O
.	O
</s>
<s>
Most	O
UML	B-Protocol
tools	I-Protocol
support	O
both	O
the	O
text	O
writing	O
and	O
visual	B-Language
modeling	I-Language
of	O
use	B-Architecture
cases	I-Architecture
.	O
</s>
