<s>
A	O
white	B-Application
pages	I-Application
schema	I-Application
is	O
a	O
data	B-Application
model	I-Application
,	O
specifically	O
a	O
logical	B-Application
schema	I-Application
,	O
for	O
organizing	O
the	O
data	O
contained	O
in	O
entries	O
in	O
a	O
directory	O
service	O
,	O
database	O
,	O
or	O
application	O
,	O
such	O
as	O
an	O
address	O
book	O
.	O
</s>
<s>
A	O
white	B-Application
pages	I-Application
schema	I-Application
typically	O
defines	O
,	O
for	O
each	O
real-world	O
object	O
being	O
represented	O
:	O
</s>
<s>
One	O
of	O
the	O
earliest	O
attempts	O
to	O
standardize	O
a	O
white	B-Application
pages	I-Application
schema	I-Application
for	O
electronic	O
mail	O
use	O
was	O
in	O
X.520	O
and	O
X.521	O
,	O
part	O
of	O
the	O
X.500	B-Protocol
specifications	O
,	O
</s>
<s>
that	O
was	O
derived	O
from	O
the	O
addressing	O
requirements	O
of	O
X.400	B-Protocol
and	O
defined	O
a	O
Directory	O
Information	O
Tree	O
that	O
mirrored	O
the	O
international	O
telephone	O
system	O
,	O
with	O
entries	O
representing	O
residential	O
and	O
organizational	O
subscribers	O
.	O
</s>
<s>
This	O
evolved	O
into	O
the	O
Lightweight	B-Protocol
Directory	I-Protocol
Access	I-Protocol
Protocol	I-Protocol
standard	O
schema	O
in	O
.	O
</s>
<s>
for	O
representing	O
individuals	O
in	O
an	O
organizational	O
context	O
is	O
inetOrgPerson	O
,	O
defined	O
in	O
,	O
although	O
versions	O
of	O
Active	B-Protocol
Directory	I-Protocol
require	O
a	O
different	O
object	O
class	O
,	O
User	O
.	O
</s>
<s>
also	O
defined	O
their	O
own	O
white	B-Application
pages	I-Application
schemas	I-Application
for	O
their	O
employees	O
or	O
customers	O
,	O
as	O
part	O
of	O
their	O
Identity	O
management	O
architecture	O
.	O
</s>
<s>
function	O
of	O
a	O
Metadirectory	B-General_Concept
,	O
and	O
data	O
interchange	O
standards	O
such	O
as	O
Common	B-Protocol
Indexing	I-Protocol
Protocol	I-Protocol
.	O
</s>
<s>
Some	O
early	O
directory	O
deployments	O
suffered	O
due	O
to	O
poor	O
design	O
choices	O
in	O
their	O
white	B-Application
pages	I-Application
schema	I-Application
,	O
such	O
as	O
:	O
</s>
<s>
Examples	O
of	O
other	O
generic	O
white	B-Application
pages	I-Application
schemas	I-Application
include	O
vCard	O
,	O
defined	O
in	O
,	O
and	O
FOAF	O
.	O
</s>
