<s>
In	O
relational	B-Application
databases	I-Application
,	O
relvar	B-Application
is	O
a	O
term	O
introduced	O
by	O
C	O
.	O
J	O
.	O
</s>
<s>
Date	O
and	O
Hugh	O
Darwen	O
as	O
an	O
abbreviation	O
for	O
relation	B-Language
variable	I-Language
in	O
their	O
1995	O
paper	O
The	O
Third	O
Manifesto	O
,	O
to	O
avoid	O
the	O
confusion	O
sometimes	O
arising	O
from	O
the	O
use	O
of	O
the	O
term	O
relation	O
,	O
by	O
the	O
inventor	O
of	O
the	O
relational	B-Architecture
model	I-Architecture
,	O
E	O
.	O
F	O
.	O
Codd	O
,	O
for	O
a	O
variable	O
to	O
which	O
a	O
relation	O
is	O
assigned	O
as	O
well	O
as	O
for	O
the	O
relation	O
itself	O
.	O
</s>
<s>
A	O
closely	O
related	O
term	O
often	O
used	O
in	O
academic	O
texts	O
is	O
relation	B-Language
schema	I-Language
,	O
this	O
being	O
a	O
set	O
of	O
attributes	O
paired	O
with	O
a	O
set	O
of	O
constraints	O
,	O
together	O
defining	O
a	O
set	O
of	O
relations	O
for	O
the	O
purpose	O
of	O
some	O
discussion	O
(	O
typically	O
,	O
database	B-Application
normalization	I-Application
)	O
.	O
</s>
<s>
Constraints	O
that	O
mention	O
just	O
one	O
relvar	B-Application
are	O
termed	O
relvar	B-Application
constraints	O
,	O
so	O
relation	B-Language
schema	I-Language
can	O
be	O
regarded	O
as	O
a	O
single	O
term	O
encompassing	O
a	O
relvar	B-Application
and	O
its	O
relvar	B-Application
constraints	O
.	O
</s>
