<s>
A	O
reference	B-Application
dimension	I-Application
is	O
a	O
dimension	O
on	O
an	O
engineering	B-Architecture
drawing	I-Architecture
provided	O
for	O
information	O
only	O
.	O
</s>
<s>
Reference	B-Application
dimensions	I-Application
are	O
provided	O
for	O
a	O
variety	O
of	O
reasons	O
and	O
are	O
often	O
an	O
accumulation	O
of	O
other	O
dimensions	O
that	O
are	O
defined	O
elsewhere	O
(	O
e.g.	O
</s>
<s>
Reference	B-Application
dimensions	I-Application
are	O
not	O
intended	O
to	O
be	O
used	O
directly	O
to	O
define	O
the	O
geometry	O
of	O
an	O
object	O
.	O
</s>
<s>
Reference	B-Application
dimensions	I-Application
do	O
not	O
normally	O
govern	O
manufacturing	O
operations	O
(	O
such	O
as	O
machining	O
)	O
in	O
any	O
way	O
and	O
,	O
therefore	O
,	O
do	O
not	O
typically	O
include	O
a	O
dimensional	O
tolerance	O
(	O
though	O
a	O
tolerance	O
may	O
be	O
provided	O
if	O
such	O
information	O
is	O
deemed	O
helpful	O
)	O
.	O
</s>
<s>
Consequently	O
,	O
reference	B-Application
dimensions	I-Application
are	O
also	O
not	O
subject	O
to	O
dimensional	O
inspection	O
under	O
normal	O
circumstances	O
.	O
</s>
<s>
Reference	B-Application
dimensions	I-Application
are	O
commonly	O
used	O
in	O
CAD	B-Application
software	I-Application
along	O
with	O
constraints	B-Algorithm
that	O
usually	O
denote	O
the	O
opposite	O
:	O
mandatory	O
dimensions	O
to	O
be	O
precisely	O
followed	O
.	O
</s>
<s>
In	O
Computer-Aided	B-Application
Design	I-Application
(	O
CAD	B-Application
)	O
it	O
's	O
commonly	O
used	O
to	O
denote	O
dimensions	O
.	O
</s>
<s>
Prior	O
to	O
use	O
of	O
modern	O
CAD	B-Application
software	I-Application
,	O
reference	B-Application
dimensions	I-Application
were	O
traditionally	O
indicated	O
on	O
a	O
drawing	O
by	O
the	O
abbreviation	O
"	O
REF	O
"	O
written	O
adjacent	O
to	O
the	O
dimension	O
(	O
typically	O
to	O
the	O
right	O
or	O
underneath	O
the	O
dimension	O
)	O
.	O
</s>
<s>
This	O
implementation	O
has	O
followed	O
in	O
modern	O
CAD	B-Application
software	I-Application
that	O
makes	O
use	O
of	O
parentheses	O
as	O
the	O
default	O
denotation	O
method	O
whenever	O
reference	B-Application
dimensions	I-Application
are	O
"	O
automatically	O
"	O
created	O
by	O
the	O
software	O
.	O
</s>
<s>
The	O
method	O
for	O
identifying	O
a	O
reference	B-Application
dimension	I-Application
(	O
or	O
reference	O
data	O
)	O
on	O
drawings	O
is	O
to	O
enclose	O
the	O
dimension	O
(	O
or	O
data	O
)	O
within	O
parentheses	O
.	O
</s>
