<s>
Windows	B-Application
Installer	I-Application
(	O
msiexec.exe	B-Application
,	O
previously	O
known	O
as	O
Microsoft	B-Application
Installer	I-Application
,	O
codename	B-General_Concept
Darwin	O
)	O
is	O
a	O
software	O
component	O
and	O
application	B-Application
programming	I-Application
interface	I-Application
(	O
API	B-Application
)	O
of	O
Microsoft	B-Application
Windows	I-Application
used	O
for	O
the	O
installation	B-Application
,	O
maintenance	O
,	O
and	O
removal	O
of	O
software	O
.	O
</s>
<s>
The	O
installation	B-Application
information	O
,	O
and	O
optionally	O
the	O
files	B-Operating_System
themselves	O
,	O
are	O
packaged	O
in	O
installation	B-Application
packages	O
,	O
loosely	O
relational	B-Application
databases	I-Application
structured	O
as	O
COM	B-Library
Structured	I-Library
Storages	I-Library
and	O
commonly	O
known	O
as	O
"	O
MSI	O
files	B-Operating_System
"	O
,	O
from	O
their	O
default	O
filename	O
extensions	O
.	O
</s>
<s>
The	O
packages	O
with	O
the	O
file	O
extensions	O
mst	O
contain	O
Windows	B-Application
Installer	I-Application
"	O
Transformation	O
Scripts	O
"	O
,	O
those	O
with	O
the	O
msm	O
extensions	O
contain	O
"	O
Merge	B-Device
Modules	I-Device
"	O
and	O
the	O
file	O
extension	O
pcp	O
is	O
used	O
for	O
"	O
Patch	O
Creation	O
Properties	O
"	O
.	O
</s>
<s>
Windows	B-Application
Installer	I-Application
contains	O
significant	O
changes	O
from	O
its	O
predecessor	O
,	O
Setup	B-Application
API	I-Application
.	O
</s>
<s>
New	O
features	O
include	O
a	O
GUI	B-Application
framework	B-Architecture
and	O
automatic	O
generation	O
of	O
the	O
uninstallation	B-Application
sequence	O
.	O
</s>
<s>
Windows	B-Application
Installer	I-Application
is	O
positioned	O
as	O
an	O
alternative	O
to	O
stand-alone	O
executable	O
installer	B-Operating_System
frameworks	O
such	O
as	O
older	O
versions	O
of	O
InstallShield	B-Application
and	O
NSIS	B-Language
.	O
</s>
<s>
Before	O
the	O
introduction	O
of	O
Microsoft	B-Application
Store	I-Application
(	O
then	O
named	O
Windows	B-Application
Store	I-Application
)	O
,	O
Microsoft	O
encouraged	O
third	O
parties	O
to	O
use	O
Windows	B-Application
Installer	I-Application
as	O
the	O
basis	O
for	O
installation	B-Application
frameworks	O
,	O
so	O
that	O
they	O
synchronize	O
correctly	O
with	O
other	O
installers	B-Operating_System
and	O
keep	O
the	O
internal	O
database	O
of	O
installed	O
products	O
consistent	O
.	O
</s>
<s>
Important	O
features	O
such	O
as	O
rollback	B-Application
and	O
versioning	B-Architecture
depend	O
on	O
a	O
consistent	O
internal	O
database	O
for	O
reliable	O
operation	O
.	O
</s>
<s>
Furthermore	O
,	O
Windows	B-Application
Installer	I-Application
facilitates	O
the	O
principle	O
of	O
least	O
privilege	O
by	O
performing	O
software	B-Application
installations	I-Application
by	O
proxy	O
for	O
unprivileged	O
users	O
.	O
</s>
<s>
A	O
package	O
describes	O
the	O
installation	B-Application
of	O
one	O
or	O
more	O
full	O
products	O
and	O
is	O
universally	O
identified	O
by	O
a	O
GUID	O
.	O
</s>
<s>
Windows	B-Application
Installer	I-Application
does	O
not	O
handle	O
dependencies	O
between	O
products	O
.	O
</s>
<s>
The	O
GUID	O
,	O
in	O
combination	O
with	O
the	O
version	O
number	O
(	O
ProductVersion	O
property	O
)	O
,	O
allows	O
for	O
release	O
management	O
of	O
the	O
product	O
's	O
files	B-Operating_System
and	O
registry	B-Protocol
keys	I-Protocol
.	O
</s>
<s>
More	O
complex	O
installers	B-Operating_System
may	O
display	O
a	O
"	O
custom	O
setup	O
"	O
dialog	O
box	O
,	O
from	O
which	O
the	O
user	O
can	O
select	O
which	O
features	O
to	O
install	O
or	O
remove	O
.	O
</s>
<s>
A	O
word	B-General_Concept
processor	I-General_Concept
,	O
for	O
example	O
,	O
might	O
place	O
the	O
program	O
's	O
core	O
file	O
into	O
one	O
feature	O
,	O
and	O
the	O
program	O
's	O
help	O
files	B-Operating_System
,	O
optional	O
spelling	O
checker	O
and	O
stationery	O
modules	O
into	O
additional	O
features	O
.	O
</s>
<s>
Each	O
component	O
is	O
treated	O
by	O
Windows	B-Application
Installer	I-Application
as	O
a	O
unit	O
.	O
</s>
<s>
The	O
installer	B-Operating_System
cannot	O
install	O
just	O
part	O
of	O
a	O
component	O
.	O
</s>
<s>
Components	O
can	O
contain	O
program	O
files	B-Operating_System
,	O
folders	B-Application
,	O
COM	B-Application
components	O
,	O
registry	B-Protocol
keys	I-Protocol
,	O
and	O
shortcuts	O
.	O
</s>
<s>
Components	O
are	O
identified	O
globally	O
by	O
GUIDs	O
;	O
thus	O
the	O
same	O
component	O
can	O
be	O
shared	O
among	O
several	O
features	O
of	O
the	O
same	O
package	O
or	O
multiple	O
packages	O
,	O
ideally	O
through	O
the	O
use	O
of	O
Merge	B-Device
Modules	I-Device
.	O
</s>
<s>
A	O
key	O
path	O
is	O
a	O
specific	O
file	O
,	O
registry	B-Protocol
key	I-Protocol
,	O
or	O
ODBC	B-Application
data	O
source	O
that	O
the	O
package	O
author	O
specifies	O
as	O
critical	O
for	O
a	O
given	O
component	O
.	O
</s>
<s>
When	O
an	O
MSI-based	O
program	O
is	O
launched	O
,	O
Windows	B-Application
Installer	I-Application
checks	O
the	O
existence	O
of	O
key	O
paths	O
.	O
</s>
<s>
Creating	O
an	O
installer	B-Operating_System
package	O
for	O
a	O
new	O
application	O
is	O
not	O
trivial	O
.	O
</s>
<s>
It	O
is	O
necessary	O
to	O
specify	O
which	O
files	B-Operating_System
must	O
be	O
installed	O
,	O
to	O
where	O
and	O
with	O
what	O
registry	B-Protocol
keys	I-Protocol
.	O
</s>
<s>
There	O
are	O
a	O
number	O
of	O
commercial	O
and	O
freeware	B-License
products	O
to	O
assist	O
in	O
creating	O
MSI	O
packages	O
,	O
including	O
Visual	B-Application
Studio	I-Application
(	O
natively	O
up	O
to	O
VS	O
2010	O
,	O
with	O
an	O
extension	O
on	O
newer	O
VS	O
versions	O
)	O
,	O
InstallShield	B-Application
and	O
WiX	B-Language
.	O
</s>
<s>
To	O
varying	O
degrees	O
,	O
the	O
user	O
interface	O
and	O
behavior	O
may	O
be	O
configured	O
for	O
use	O
in	O
less	O
common	O
situations	O
such	O
as	O
unattended	O
installation	B-Application
.	O
</s>
<s>
Once	O
prepared	O
,	O
an	O
installer	B-Operating_System
package	O
is	O
"	O
compiled	O
"	O
by	O
reading	O
the	O
instructions	O
and	O
files	B-Operating_System
from	O
the	O
developer	O
's	O
local	O
machine	O
,	O
and	O
creating	O
the	O
.msi	B-Application
file	O
.	O
</s>
<s>
The	O
user	O
interface	O
(	O
dialog	O
boxes	O
)	O
presented	O
at	O
the	O
start	O
of	O
installation	B-Application
can	O
be	O
changed	O
or	O
configured	O
by	O
the	O
setup	O
engineer	O
developing	O
a	O
new	O
installer	B-Operating_System
.	O
</s>
<s>
An	O
installer	B-Operating_System
package	O
should	O
be	O
capable	O
of	O
running	O
without	O
any	O
UI	O
,	O
for	O
what	O
is	O
called	O
"	O
unattended	O
installation	B-Application
"	O
.	O
</s>
<s>
The	O
ICE	O
rules	O
are	O
combined	O
into	O
CUB	O
files	B-Operating_System
,	O
which	O
are	O
stripped-down	O
MSI	O
files	B-Operating_System
containing	O
custom	O
actions	O
that	O
test	O
the	O
target	O
MSI	O
database	O
's	O
contents	O
for	O
validation	O
warnings	O
and	O
errors	O
.	O
</s>
<s>
ICE33	O
:	O
Validates	O
that	O
the	O
Registry	B-Protocol
table	O
is	O
not	O
used	O
for	O
data	O
better	O
suited	O
for	O
another	O
table	O
(	O
Class	O
,	O
Extension	O
,	O
Verb	O
,	O
and	O
so	O
on	O
)	O
.	O
</s>
