<s>
In	O
computer	B-General_Concept
science	I-General_Concept
,	O
a	O
U-form	B-Application
is	O
an	O
abstract	O
data	O
type	O
comprising	O
a	O
collection	B-Application
of	O
attribute	B-Application
–	I-Application
value	I-Application
pairs	I-Application
associated	O
with	O
a	O
universally-unique	O
identifier	O
(	O
UUID	O
)	O
.	O
</s>
<s>
A	O
U-form	B-Application
essentially	O
comprises	O
an	O
associative	B-Application
array	I-Application
augmented	O
with	O
a	O
UUID	O
and	O
with	O
keys	O
limited	O
to	O
strings	O
.	O
</s>
<s>
The	O
UUID	O
that	O
is	O
associated	O
with	O
a	O
u-form	B-Application
is	O
immutable	O
,	O
however	O
all	O
data	O
"	O
contained	O
"	O
in	O
the	O
u-form	B-Application
are	O
mutable	O
(	O
including	O
the	O
keys/names	O
)	O
.	O
</s>
<s>
Navigational	B-General_Concept
databases	I-General_Concept
,	O
Entity	B-Architecture
and	O
associative	B-Application
entity	I-Application
relationships	O
can	O
be	O
implemented	O
by	O
using	O
a	O
UUID	O
,	O
or	O
multiple	O
UUIDs	O
,	O
as	O
attribute	O
values	O
.	O
</s>
<s>
The	O
u-form	B-Application
'	O
s	O
design	O
goals	O
center	O
around	O
supporting	O
an	O
open	O
,	O
extensible	O
distributed	O
information	O
space	O
,	O
emphasizing	O
the	O
unambiguous	O
identity	O
of	O
data	O
objects	O
and	O
the	O
separation	O
between	O
data	O
storage	O
,	O
data	O
characterization	O
,	O
and	O
schema	O
development	O
.	O
</s>
<s>
The	O
use	O
of	O
non-semantic	O
UUIDs	O
combined	O
with	O
a	O
simple	O
attribute	B-Application
–	I-Application
value	I-Application
model	O
draws	O
a	O
clear	O
distinction	O
between	O
identity	O
and	O
data	O
.	O
</s>
<s>
Although	O
u-forms	B-Application
share	O
certain	O
design	O
characteristics	O
with	O
serialization	O
formats	O
such	O
as	O
XML	B-Protocol
,	O
they	O
should	O
not	O
be	O
confused	O
with	O
such	O
representational	O
formats	O
.	O
</s>
<s>
Since	O
u-forms	B-Application
are	O
abstract	O
,	O
they	O
do	O
not	O
specify	O
any	O
particular	O
representational	O
format	O
.	O
</s>
<s>
Indeed	O
,	O
they	O
may	O
be	O
stored	O
as	O
or	O
communicated	O
via	O
XML	B-Protocol
or	O
other	O
types	O
of	O
serialization	O
.	O
</s>
<s>
The	O
operations	O
defined	O
for	O
a	O
u-form	B-Application
are	O
similar	O
to	O
associative	B-Application
arrays	I-Application
:	O
</s>
<s>
U-forms	B-Application
have	O
the	O
following	O
properties	O
:	O
</s>
<s>
An	O
important	O
characteristic	O
of	O
u-forms	B-Application
,	O
of	O
significance	O
to	O
distributed	B-Operating_System
database	I-Operating_System
systems	I-Operating_System
,	O
is	O
that	O
they	O
support	O
a	O
clear	O
distinction	O
between	O
copying	O
and	O
replication	O
of	O
data	O
objects	O
.	O
</s>
<s>
Copying	O
a	O
u-form	B-Application
involves	O
the	O
creation	O
of	O
a	O
new	O
u-form	B-Application
(	O
i.e.	O
,	O
one	O
with	O
a	O
different	O
UUID	O
)	O
,	O
but	O
with	O
all	O
attribute	B-Application
–	I-Application
value	I-Application
pairs	I-Application
identical	O
to	O
those	O
of	O
the	O
original	O
u-form	B-Application
.	O
</s>
<s>
Replicating	O
a	O
u-form	B-Application
involves	O
creating	O
a	O
new	O
instance	O
of	O
the	O
u-form	B-Application
with	O
the	O
same	O
UUID	O
as	O
the	O
original	O
.	O
</s>
<s>
Note	O
that	O
in	O
a	O
distributed	O
system	O
,	O
two	O
instances	O
of	O
the	O
same	O
u-form	B-Application
may	O
be	O
inconsistent	O
(	O
i.e.	O
,	O
they	O
may	O
contain	O
different	O
attribute	B-Application
–	I-Application
value	I-Application
pairs	I-Application
)	O
.	O
</s>
<s>
U-forms	B-Application
were	O
developed	O
at	O
MAYA	O
Design	O
as	O
part	O
of	O
the	O
Visage	O
Information	O
Visualization	O
System	O
,	O
a	O
joint	O
project	O
of	O
MAYA	O
and	O
Carnegie	O
Mellon	O
University	O
funded	O
by	O
DARPA	O
and	O
The	O
Army	O
Research	O
Laboratory	O
.	O
</s>
<s>
The	O
name	O
"	O
u-form	B-Application
"	O
derives	O
from	O
the	O
term	O
"	O
e-form	O
"	O
,	O
a	O
hypothetical	O
"	O
electronic	O
form	O
"	O
proposed	O
by	O
Michael	O
Dertouzos	O
in	O
his	O
1997	O
book	O
"	O
What	O
Will	O
Be	O
"	O
.	O
</s>
<s>
and	O
large-scale	O
production	O
systems	O
,	O
most	O
notably	O
the	O
US	O
Army	O
's	O
Command	B-Protocol
Post	I-Protocol
of	I-Protocol
the	I-Protocol
Future	I-Protocol
.	O
</s>
