<s>
Software	B-Architecture
architecture	I-Architecture
is	O
the	O
set	O
of	O
structures	O
needed	O
to	O
reason	O
about	O
a	O
software	O
system	O
and	O
the	O
discipline	O
of	O
creating	O
such	O
structures	O
and	O
systems	O
.	O
</s>
<s>
It	O
functions	O
as	O
the	O
blueprints	B-Application
for	O
the	O
system	O
and	O
the	O
development	O
project	O
,	O
which	O
project	O
management	O
can	O
later	O
use	O
to	O
extrapolate	O
the	O
tasks	O
necessary	O
to	O
be	O
executed	O
by	O
the	O
teams	O
and	O
people	O
involved	O
.	O
</s>
<s>
Software	B-Architecture
architecture	I-Architecture
is	O
about	O
making	O
fundamental	O
structural	O
choices	O
that	O
are	O
costly	O
to	O
change	O
once	O
implemented	O
.	O
</s>
<s>
Software	B-Architecture
architecture	I-Architecture
choices	O
include	O
specific	O
structural	O
options	O
from	O
possibilities	O
in	O
the	O
design	O
of	O
the	O
software	O
.	O
</s>
<s>
Therefore	O
,	O
an	O
appropriate	O
real-time	B-General_Concept
computing	I-General_Concept
language	O
would	O
need	O
to	O
be	O
chosen	O
.	O
</s>
<s>
Documenting	O
software	B-Architecture
architecture	I-Architecture
facilitates	O
communication	O
between	O
stakeholders	O
,	O
captures	O
early	O
decisions	O
about	O
the	O
high-level	O
design	O
,	O
and	O
allows	O
reuse	O
of	O
design	O
components	O
between	O
projects	O
.	O
</s>
<s>
Opinions	O
vary	O
as	O
to	O
the	O
scope	O
of	O
software	B-Architecture
architectures	I-Architecture
:	O
</s>
<s>
Macroscopic	O
system	O
structure	O
:	O
this	O
refers	O
to	O
architecture	O
as	O
a	O
higher-level	O
abstraction	B-Application
of	O
a	O
software	O
system	O
that	O
consists	O
of	O
a	O
collection	O
of	O
computational	O
components	O
together	O
with	O
connectors	O
that	O
describe	O
the	O
interaction	O
between	O
these	O
components	O
.	O
</s>
<s>
The	O
important	O
stuff	O
—	O
whatever	O
that	O
is	O
:	O
this	O
refers	O
to	O
the	O
fact	O
that	O
software	B-Architecture
architects	I-Architecture
should	O
concern	O
themselves	O
with	O
those	O
decisions	O
that	O
have	O
high	O
impact	O
on	O
the	O
system	O
and	O
its	O
stakeholders	O
.	O
</s>
<s>
A	O
set	O
of	O
architectural	O
design	O
decisions	O
:	O
software	B-Architecture
architecture	I-Architecture
should	O
not	O
be	O
considered	O
merely	O
a	O
set	O
of	O
models	O
or	O
structures	O
,	O
but	O
should	O
include	O
the	O
decisions	O
that	O
lead	O
to	O
these	O
particular	O
structures	O
,	O
and	O
the	O
rationale	O
behind	O
them	O
.	O
</s>
<s>
This	O
insight	O
has	O
led	O
to	O
substantial	O
research	O
into	O
software	B-Architecture
architecture	I-Architecture
knowledge	O
management	O
.	O
</s>
<s>
There	O
is	O
no	O
sharp	O
distinction	O
between	O
software	B-Architecture
architecture	I-Architecture
versus	O
design	O
and	O
requirements	O
engineering	O
(	O
see	O
Related	O
fields	O
below	O
)	O
.	O
</s>
<s>
Software	B-Architecture
architecture	I-Architecture
exhibits	O
the	O
following	O
:	O
</s>
<s>
These	O
separate	O
descriptions	O
are	O
called	O
architectural	O
views	B-Architecture
(	O
see	O
for	O
example	O
the	O
4+1	B-Architecture
architectural	I-Architecture
view	I-Architecture
model	I-Architecture
)	O
.	O
</s>
<s>
Jackson	B-Application
Structured	I-Application
Programming	I-Application
)	O
were	O
driven	O
by	O
required	O
functionality	O
and	O
the	O
flow	O
of	O
data	O
through	O
the	O
system	O
,	O
but	O
the	O
current	O
insight	O
is	O
that	O
the	O
architecture	O
of	O
a	O
software	O
system	O
is	O
more	O
closely	O
related	O
to	O
its	O
quality	O
attributes	O
such	O
as	O
fault-tolerance	B-General_Concept
,	O
backward	B-General_Concept
compatibility	I-General_Concept
,	O
extensibility	B-Architecture
,	O
reliability	O
,	O
maintainability	O
,	O
availability	O
,	O
security	O
,	O
usability	O
,	O
and	O
other	O
such	O
–	O
ilities	O
.	O
</s>
<s>
Recurring	O
styles	O
:	O
like	O
building	O
architecture	O
,	O
the	O
software	B-Architecture
architecture	I-Architecture
discipline	O
has	O
developed	O
standard	O
ways	O
to	O
address	O
recurring	O
concerns	O
.	O
</s>
<s>
These	O
"	O
standard	O
ways	O
"	O
are	O
called	O
by	O
various	O
names	O
at	O
various	O
levels	O
of	O
abstraction	B-Application
.	O
</s>
<s>
Common	O
terms	O
for	O
recurring	O
solutions	O
are	O
architectural	O
style	O
,	O
tactic	O
,	O
reference	B-Architecture
architecture	I-Architecture
and	O
architectural	O
pattern	O
.	O
</s>
<s>
Software	B-Architecture
architecture	I-Architecture
is	O
an	O
"	O
intellectually	O
graspable	O
"	O
abstraction	B-Application
of	O
a	O
complex	O
system	O
.	O
</s>
<s>
This	O
abstraction	B-Application
provides	O
a	O
number	O
of	O
benefits	O
:	O
</s>
<s>
A	O
number	O
of	O
techniques	O
have	O
been	O
developed	O
to	O
perform	O
such	O
analyses	O
,	O
such	O
as	O
ATAM	B-Architecture
or	O
by	O
creating	O
a	O
visual	O
representation	O
of	O
the	O
software	O
system	O
.	O
</s>
<s>
A	O
complete	O
software	B-Architecture
architecture	I-Architecture
or	O
parts	O
of	O
it	O
,	O
like	O
individual	O
architectural	O
strategies	O
and	O
decisions	O
,	O
can	O
be	O
re-used	O
across	O
multiple	O
systems	O
whose	O
stakeholders	O
require	O
similar	O
quality	O
attributes	O
or	O
functionality	O
,	O
saving	O
design	O
costs	O
and	O
mitigating	O
the	O
risk	O
of	O
design	O
mistakes	O
.	O
</s>
<s>
Software	B-Architecture
architecture	I-Architecture
helps	O
to	O
reduce	O
risks	O
and	O
chance	O
of	O
failure	O
.	O
</s>
<s>
Software	B-Architecture
architecture	I-Architecture
is	O
a	O
means	O
to	O
manage	O
risk	O
and	O
costs	O
in	O
complex	O
IT	O
projects	O
.	O
</s>
<s>
The	O
comparison	O
between	O
software	O
design	O
and	O
(	O
civil	O
)	O
architecture	O
was	O
first	O
drawn	O
in	O
the	O
late	O
1960s	O
,	O
but	O
the	O
term	O
"	O
software	B-Architecture
architecture	I-Architecture
"	O
did	O
not	O
see	O
widespread	O
usage	O
until	O
the	O
1990s	O
.	O
</s>
<s>
The	O
field	O
of	O
computer	B-General_Concept
science	I-General_Concept
had	O
encountered	O
problems	O
associated	O
with	O
complexity	O
since	O
its	O
formation	O
.	O
</s>
<s>
Earlier	O
problems	O
of	O
complexity	O
were	O
solved	O
by	O
developers	O
by	O
choosing	O
the	O
right	O
data	B-General_Concept
structures	I-General_Concept
,	O
developing	O
algorithms	O
,	O
and	O
by	O
applying	O
the	O
concept	O
of	O
separation	O
of	O
concerns	O
.	O
</s>
<s>
Although	O
the	O
term	O
"	O
software	B-Architecture
architecture	I-Architecture
"	O
is	O
relatively	O
new	O
to	O
the	O
industry	O
,	O
the	O
fundamental	O
principles	O
of	O
the	O
field	O
have	O
been	O
applied	O
sporadically	O
by	O
software	B-General_Concept
engineering	I-General_Concept
pioneers	O
since	O
the	O
mid-1980s	O
.	O
</s>
<s>
Early	O
attempts	O
to	O
capture	O
and	O
explain	O
software	B-Architecture
architecture	I-Architecture
of	O
a	O
system	O
were	O
imprecise	O
and	O
disorganized	O
,	O
often	O
characterized	O
by	O
a	O
set	O
of	O
box-and-line	O
diagrams	O
.	O
</s>
<s>
Software	B-Architecture
architecture	I-Architecture
as	O
a	O
concept	O
has	O
its	O
origins	O
in	O
the	O
research	O
of	O
Edsger	O
Dijkstra	O
in	O
1968	O
and	O
David	O
Parnas	O
in	O
the	O
early	O
1970s	O
.	O
</s>
<s>
During	O
the	O
1990s	O
there	O
was	O
a	O
concerted	O
effort	O
to	O
define	O
and	O
codify	O
fundamental	O
aspects	O
of	O
the	O
discipline	O
,	O
with	O
research	O
work	O
concentrating	O
on	O
architectural	O
styles	O
(	O
patterns	O
)	O
,	O
architecture	B-Architecture
description	I-Architecture
languages	I-Architecture
,	O
architecture	O
documentation	O
,	O
and	O
formal	B-Architecture
methods	I-Architecture
.	O
</s>
<s>
Research	O
institutions	O
have	O
played	O
a	O
prominent	O
role	O
in	O
furthering	O
software	B-Architecture
architecture	I-Architecture
as	O
a	O
discipline	O
.	O
</s>
<s>
Mary	O
Shaw	O
and	O
David	O
Garlan	O
of	O
Carnegie	O
Mellon	O
wrote	O
a	O
book	O
titled	O
Software	B-Architecture
Architecture	I-Architecture
:	O
Perspectives	O
on	O
an	O
Emerging	O
Discipline	O
in	O
1996	O
,	O
which	O
promoted	O
software	B-Architecture
architecture	I-Architecture
concepts	O
such	O
as	O
components	O
,	O
connectors	O
,	O
and	O
styles	O
.	O
</s>
<s>
The	O
University	O
of	O
California	O
,	O
Irvine	O
's	O
Institute	O
for	O
Software	O
Research	O
's	O
efforts	O
in	O
software	B-Architecture
architecture	I-Architecture
research	O
is	O
directed	O
primarily	O
in	O
architectural	O
styles	O
,	O
architecture	B-Architecture
description	I-Architecture
languages	I-Architecture
,	O
and	O
dynamic	O
architectures	O
.	O
</s>
<s>
IEEE	O
1471-2000	O
,	O
"	O
Recommended	O
Practice	O
for	O
Architecture	O
Description	O
of	O
Software-Intensive	O
Systems	O
"	O
,	O
was	O
the	O
first	O
formal	O
standard	O
in	O
the	O
area	O
of	O
software	B-Architecture
architecture	I-Architecture
.	O
</s>
<s>
It	O
was	O
adopted	O
in	O
2007	O
by	O
ISO	O
as	O
ISO/IEC	B-Architecture
42010:2007	I-Architecture
.	O
</s>
<s>
In	O
November	O
2011	O
,	O
IEEE	B-Architecture
1471	I-Architecture
–	O
2000	O
was	O
superseded	O
by	O
ISO/IEC/IEEE	O
42010:2011	O
,	O
"	O
Systems	O
and	O
software	B-General_Concept
engineering	I-General_Concept
–	O
Architecture	O
description	O
"	O
(	O
jointly	O
published	O
by	O
IEEE	O
and	O
ISO	O
)	O
.	O
</s>
<s>
While	O
in	O
IEEE	B-Architecture
1471	I-Architecture
,	O
software	B-Architecture
architecture	I-Architecture
was	O
about	O
the	O
architecture	O
of	O
"	O
software-intensive	O
systems	O
"	O
,	O
defined	O
as	O
"	O
any	O
system	O
where	O
software	O
contributes	O
essential	O
influences	O
to	O
the	O
design	O
,	O
construction	O
,	O
deployment	O
,	O
and	O
evolution	O
of	O
the	O
system	O
as	O
a	O
whole	O
"	O
,	O
the	O
2011	O
edition	O
goes	O
a	O
step	O
further	O
by	O
including	O
the	O
ISO/IEC	O
15288	O
and	O
ISO/IEC	O
12207	O
definitions	O
of	O
a	O
system	O
,	O
which	O
embrace	O
not	O
only	O
hardware	O
and	O
software	O
,	O
but	O
also	O
"	O
humans	O
,	O
processes	O
,	O
procedures	O
,	O
facilities	O
,	O
materials	O
and	O
naturally	O
occurring	O
entities	O
"	O
.	O
</s>
<s>
This	O
reflects	O
the	O
relationship	O
between	O
software	B-Architecture
architecture	I-Architecture
,	O
enterprise	O
architecture	O
and	O
solution	B-Architecture
architecture	I-Architecture
.	O
</s>
<s>
There	O
are	O
many	O
activities	O
that	O
a	O
software	B-Architecture
architect	I-Architecture
performs	O
.	O
</s>
<s>
A	O
software	B-Architecture
architect	I-Architecture
typically	O
works	O
with	O
project	O
managers	O
,	O
discusses	O
architecturally	B-Architecture
significant	I-Architecture
requirements	I-Architecture
with	O
stakeholders	O
,	O
designs	O
a	O
software	B-Architecture
architecture	I-Architecture
,	O
evaluates	O
a	O
design	O
,	O
communicates	O
with	O
designers	O
and	O
stakeholders	O
,	O
documents	O
the	O
architectural	O
design	O
and	O
more	O
.	O
</s>
<s>
There	O
are	O
four	O
core	O
activities	O
in	O
software	B-Architecture
architecture	I-Architecture
design	O
.	O
</s>
<s>
The	O
outputs	O
of	O
the	O
analysis	O
activity	O
are	O
those	O
requirements	O
that	O
have	O
a	O
measurable	O
impact	O
on	O
a	O
software	O
system	O
's	O
architecture	O
,	O
called	O
architecturally	B-Architecture
significant	I-Architecture
requirements	I-Architecture
.	O
</s>
<s>
Given	O
the	O
architecturally	B-Architecture
significant	I-Architecture
requirements	I-Architecture
determined	O
by	O
the	O
analysis	O
,	O
the	O
current	O
state	O
of	O
the	O
design	O
and	O
the	O
results	O
of	O
any	O
evaluation	O
activities	O
,	O
the	O
design	O
is	O
created	O
and	O
improved	O
.	O
</s>
<s>
Some	O
of	O
the	O
available	O
software	B-Architecture
architecture	I-Architecture
evaluation	O
techniques	O
include	O
Architecture	B-Architecture
Tradeoff	I-Architecture
Analysis	I-Architecture
Method	I-Architecture
(	O
ATAM	B-Architecture
)	O
and	O
TARA	O
.	O
</s>
<s>
Frameworks	B-Architecture
for	O
comparing	O
the	O
techniques	O
are	O
discussed	O
in	O
frameworks	B-Architecture
such	O
as	O
SARA	O
Report	O
and	O
Architecture	O
Reviews	O
:	O
Practice	O
and	O
Experience	O
.	O
</s>
<s>
Architecture	O
evolution	O
is	O
the	O
process	O
of	O
maintaining	O
and	O
adapting	O
an	O
existing	O
software	B-Architecture
architecture	I-Architecture
to	O
meet	O
changes	O
in	O
requirements	O
and	O
environment	O
.	O
</s>
<s>
As	O
software	B-Architecture
architecture	I-Architecture
provides	O
a	O
fundamental	O
structure	O
of	O
a	O
software	O
system	O
,	O
its	O
evolution	O
and	O
maintenance	O
would	O
necessarily	O
impact	O
its	O
fundamental	O
structure	O
.	O
</s>
<s>
These	O
supporting	O
activities	O
take	O
place	O
throughout	O
the	O
core	O
software	B-Architecture
architecture	I-Architecture
process	O
.	O
</s>
<s>
Software	B-Architecture
architecture	I-Architecture
supporting	O
activities	O
are	O
carried	O
out	O
during	O
core	O
software	B-Architecture
architecture	I-Architecture
activities	O
.	O
</s>
<s>
These	O
supporting	O
activities	O
assist	O
a	O
software	B-Architecture
architect	I-Architecture
to	O
carry	O
out	O
analysis	O
,	O
synthesis	O
,	O
evaluation	O
,	O
and	O
evolution	O
.	O
</s>
<s>
Knowledge	O
management	O
and	O
communication	O
is	O
the	O
act	O
of	O
exploring	O
and	O
managing	O
knowledge	O
that	O
is	O
essential	O
to	O
designing	O
a	O
software	B-Architecture
architecture	I-Architecture
.	O
</s>
<s>
A	O
software	B-Architecture
architect	I-Architecture
does	O
not	O
work	O
in	O
isolation	O
.	O
</s>
<s>
Software	B-Architecture
architecture	I-Architecture
knowledge	O
is	O
often	O
tacit	O
and	O
is	O
retained	O
in	O
the	O
heads	O
of	O
stakeholders	O
.	O
</s>
<s>
Software	B-Architecture
architecture	I-Architecture
knowledge	O
management	O
activity	O
is	O
about	O
finding	O
,	O
communicating	O
,	O
and	O
retaining	O
knowledge	O
.	O
</s>
<s>
As	O
software	B-Architecture
architecture	I-Architecture
design	O
issues	O
are	O
intricate	O
and	O
interdependent	O
,	O
a	O
knowledge	O
gap	O
in	O
design	O
reasoning	O
can	O
lead	O
to	O
incorrect	O
software	B-Architecture
architecture	I-Architecture
design	O
.	O
</s>
<s>
This	O
activity	O
is	O
fundamental	O
to	O
all	O
three	O
core	O
software	B-Architecture
architecture	I-Architecture
activities	O
.	O
</s>
<s>
This	O
process	O
occurs	O
at	O
different	O
levels	O
of	O
decision	O
granularity	O
while	O
evaluating	O
significant	O
architectural	O
requirements	O
and	O
software	B-Architecture
architecture	I-Architecture
decisions	O
,	O
and	O
software	B-Architecture
architecture	I-Architecture
analysis	O
,	O
synthesis	O
,	O
and	O
evaluation	O
.	O
</s>
<s>
Documentation	O
is	O
the	O
act	O
of	O
recording	O
the	O
design	O
generated	O
during	O
the	O
software	B-Architecture
architecture	I-Architecture
process	O
.	O
</s>
<s>
System	O
design	O
is	O
described	O
using	O
several	O
views	B-Architecture
that	O
frequently	O
include	O
a	O
static	O
view	O
showing	O
the	O
code	O
structure	O
of	O
the	O
system	O
,	O
a	O
dynamic	O
view	O
showing	O
the	O
actions	O
of	O
the	O
system	O
during	O
execution	O
,	O
and	O
a	O
deployment	O
view	O
showing	O
how	O
a	O
system	O
is	O
placed	O
on	O
hardware	O
for	O
execution	O
.	O
</s>
<s>
Kruchten	O
's	O
4+1	B-Architecture
view	O
suggests	O
a	O
description	O
of	O
commonly	O
used	O
views	B-Architecture
for	O
documenting	O
software	B-Architecture
architecture	I-Architecture
;	O
Documenting	O
Software	B-Architecture
Architectures	I-Architecture
:	O
Views	B-Architecture
and	O
Beyond	O
has	O
descriptions	O
of	O
the	O
kinds	O
of	O
notations	O
that	O
could	O
be	O
used	O
within	O
the	O
view	O
description	O
.	O
</s>
<s>
Examples	O
of	O
documentation	O
activities	O
are	O
writing	O
a	O
specification	O
,	O
recording	O
a	O
system	O
design	O
model	O
,	O
documenting	O
a	O
design	O
rationale	O
,	O
developing	O
a	O
viewpoint	O
,	O
documenting	O
views	B-Architecture
.	O
</s>
<s>
Software	B-Architecture
architecture	I-Architecture
description	O
involves	O
the	O
principles	O
and	O
practices	O
of	O
modeling	O
and	O
representing	O
architectures	O
,	O
using	O
mechanisms	O
such	O
as	O
architecture	B-Architecture
description	I-Architecture
languages	I-Architecture
,	O
architecture	B-Architecture
viewpoints	I-Architecture
,	O
and	O
architecture	B-Architecture
frameworks	I-Architecture
.	O
</s>
<s>
An	O
architecture	B-Architecture
description	I-Architecture
language	I-Architecture
(	O
ADL	O
)	O
is	O
any	O
means	O
of	O
expression	O
used	O
to	O
describe	O
a	O
software	B-Architecture
architecture	I-Architecture
(	O
ISO/IEC/IEEE	O
42010	O
)	O
.	O
</s>
<s>
Many	O
special-purpose	O
ADLs	O
have	O
been	O
developed	O
since	O
the	O
1990s	O
,	O
including	O
AADL	B-Architecture
(	O
SAE	O
standard	O
)	O
,	O
Wright	B-Language
(	O
developed	O
by	O
Carnegie	O
Mellon	O
)	O
,	O
Acme	O
(	O
developed	O
by	O
Carnegie	O
Mellon	O
)	O
,	O
xADL	O
(	O
developed	O
by	O
UCI	O
)	O
,	O
Darwin	B-General_Concept
(	O
developed	O
by	O
Imperial	O
College	O
London	O
)	O
,	O
DAOP-ADL	O
(	O
developed	O
by	O
University	O
of	O
Málaga	O
)	O
,	O
SBC-ADL	O
(	O
developed	O
by	O
National	O
Sun	O
Yat-Sen	O
University	O
)	O
,	O
and	O
ByADL	O
(	O
University	O
of	O
L'Aquila	O
,	O
Italy	O
)	O
.	O
</s>
<s>
Software	B-Architecture
architecture	I-Architecture
descriptions	O
are	O
commonly	O
organized	O
into	O
views	B-Architecture
,	O
which	O
are	O
analogous	O
to	O
the	O
different	O
types	O
of	O
blueprints	B-Application
made	O
in	O
building	O
architecture	O
.	O
</s>
<s>
The	O
viewpoint	O
specifies	O
not	O
only	O
the	O
concerns	O
framed	O
(	O
i.e.	O
,	O
to	O
be	O
addressed	O
)	O
but	O
the	O
presentation	O
,	O
model	O
kinds	O
used	O
,	O
conventions	O
used	O
and	O
any	O
consistency	O
(	O
correspondence	O
)	O
rules	O
to	O
keep	O
a	O
view	O
consistent	O
with	O
other	O
views	B-Architecture
.	O
</s>
<s>
An	O
architecture	B-Architecture
framework	I-Architecture
captures	O
the	O
"	O
conventions	O
,	O
principles	O
and	O
practices	O
for	O
the	O
description	O
of	O
architectures	O
established	O
within	O
a	O
specific	O
domain	O
of	O
application	B-Application
and/or	O
community	O
of	O
stakeholders	O
"	O
(	O
ISO/IEC/IEEE	O
42010	O
)	O
.	O
</s>
<s>
An	O
architectural	O
pattern	O
is	O
a	O
general	O
,	O
reusable	O
solution	O
to	O
a	O
commonly	O
occurring	O
problem	O
in	O
software	B-Architecture
architecture	I-Architecture
within	O
a	O
given	O
context	O
.	O
</s>
<s>
There	O
are	O
also	O
concerns	O
that	O
software	B-Architecture
architecture	I-Architecture
leads	O
to	O
too	O
much	O
Big	O
Design	O
Up	O
Front	O
,	O
especially	O
among	O
proponents	O
of	O
agile	O
software	O
development	O
.	O
</s>
<s>
Software	B-Architecture
architecture	I-Architecture
erosion	O
(	O
or	O
"	O
decay	O
"	O
)	O
refers	O
to	O
the	O
gap	O
observed	O
between	O
the	O
planned	O
and	O
actual	O
architecture	O
of	O
a	O
software	O
system	O
as	O
realized	O
in	O
its	O
implementation	O
.	O
</s>
<s>
Software	B-Architecture
architecture	I-Architecture
erosion	O
occurs	O
when	O
implementation	O
decisions	O
either	O
do	O
not	O
fully	O
achieve	O
the	O
architecture-as-planned	O
or	O
otherwise	O
violate	O
constraints	O
or	O
principles	O
of	O
that	O
architecture	O
.	O
</s>
<s>
There	O
are	O
two	O
major	O
techniques	O
to	O
detect	O
architectural	O
violations	O
:	O
reflexion	O
models	O
and	O
domain-specific	B-Language
languages	I-Language
.	O
</s>
<s>
There	O
are	O
also	O
domain-specific	B-Language
languages	I-Language
with	O
a	O
focus	O
on	O
specifying	O
and	O
checking	O
architectural	O
constraints	O
.	O
</s>
<s>
Software	B-Architecture
architecture	I-Architecture
recovery	O
(	O
or	O
reconstruction	O
,	O
or	O
reverse	O
engineering	O
)	O
includes	O
the	O
methods	O
,	O
techniques	O
,	O
and	O
processes	O
to	O
uncover	O
a	O
software	O
system	O
's	O
architecture	O
from	O
available	O
information	O
,	O
including	O
its	O
implementation	O
and	O
documentation	O
.	O
</s>
<s>
Practices	O
exist	O
to	O
recover	O
software	B-Architecture
architecture	I-Architecture
as	O
static	O
program	O
analysis	O
.	O
</s>
<s>
This	O
is	O
a	O
part	O
of	O
subjects	O
covered	O
by	O
the	O
software	B-General_Concept
intelligence	I-General_Concept
practice	O
.	O
</s>
<s>
In	O
practice	O
,	O
the	O
architect	O
is	O
the	O
one	O
who	O
draws	O
the	O
line	O
between	O
software	B-Architecture
architecture	I-Architecture
(	O
architectural	O
design	O
)	O
and	O
detailed	O
design	O
(	O
non-architectural	O
design	O
)	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
client	B-Operating_System
–	I-Operating_System
server	I-Operating_System
style	O
is	O
architectural	O
(	O
strategic	O
)	O
because	O
a	O
program	O
that	O
is	O
built	O
on	O
this	O
principle	O
can	O
be	O
expanded	O
into	O
a	O
program	O
that	O
is	O
not	O
client	B-Operating_System
–	I-Operating_System
server	I-Operating_System
—	O
for	O
example	O
,	O
by	O
adding	O
peer-to-peer	O
nodes	O
.	O
</s>
<s>
Requirements	O
engineering	O
and	O
software	B-Architecture
architecture	I-Architecture
can	O
be	O
seen	O
as	O
complementary	O
approaches	O
:	O
while	O
software	B-Architecture
architecture	I-Architecture
targets	O
the	O
'	O
solution	O
space	O
 '	O
or	O
the	O
'	O
how	O
 '	O
,	O
requirements	O
engineering	O
addresses	O
the	O
'	O
problem	O
space	O
 '	O
or	O
the	O
'	O
what	O
 '	O
.	O
</s>
<s>
Both	O
requirements	O
engineering	O
and	O
software	B-Architecture
architecture	I-Architecture
revolve	O
around	O
stakeholder	O
concerns	O
,	O
needs	O
and	O
wishes	O
.	O
</s>
<s>
There	O
is	O
considerable	O
overlap	O
between	O
requirements	O
engineering	O
and	O
software	B-Architecture
architecture	I-Architecture
,	O
as	O
evidenced	O
for	O
example	O
by	O
a	O
study	O
into	O
five	O
industrial	O
software	B-Architecture
architecture	I-Architecture
methods	O
that	O
concludes	O
that	O
"	O
the	O
inputs	O
(	O
goals	O
,	O
constraints	O
,	O
etc	O
.	O
)	O
</s>
<s>
In	O
short	O
,	O
required	O
behavior	O
impacts	O
solution	B-Architecture
architecture	I-Architecture
,	O
which	O
in	O
turn	O
may	O
introduce	O
new	O
requirements	O
.	O
</s>
<s>
Approaches	O
such	O
as	O
the	O
Twin	O
Peaks	O
model	O
aim	O
to	O
exploit	O
the	O
synergistic	B-Language
relation	O
between	O
requirements	O
and	O
architecture	O
.	O
</s>
<s>
Computer	B-General_Concept
architecture	I-General_Concept
targets	O
the	O
internal	O
structure	O
of	O
a	O
computer	O
system	O
,	O
in	O
terms	O
of	O
collaborating	O
hardware	O
components	O
such	O
as	O
the	O
CPU	B-General_Concept
–	O
or	O
processor	O
–	O
the	O
bus	B-General_Concept
and	O
the	O
memory	B-General_Concept
.	O
</s>
<s>
The	O
term	O
systems	B-Architecture
architecture	I-Architecture
has	O
originally	O
been	O
applied	O
to	O
the	O
architecture	O
of	O
systems	O
that	O
consists	O
of	O
both	O
hardware	O
and	O
software	O
.	O
</s>
<s>
The	O
main	O
concern	O
addressed	O
by	O
the	O
systems	B-Architecture
architecture	I-Architecture
is	O
then	O
the	O
integration	O
of	O
software	O
and	O
hardware	O
in	O
a	O
complete	O
,	O
correctly	O
working	O
device	O
.	O
</s>
<s>
Enterprise	O
architecture	B-Architecture
frameworks	I-Architecture
,	O
such	O
as	O
TOGAF	O
and	O
the	O
Zachman	B-Library
Framework	I-Library
,	O
usually	O
distinguish	O
between	O
different	O
enterprise	O
architecture	O
layers	O
.	O
</s>
<s>
Although	O
terminology	O
differs	O
from	O
framework	O
to	O
framework	O
,	O
many	O
include	O
at	O
least	O
a	O
distinction	O
between	O
a	O
business	O
layer	O
,	O
an	O
application	B-Application
(	O
or	O
information	O
)	O
layer	O
,	O
and	O
a	O
technology	O
layer	O
.	O
</s>
