<s>
In	O
the	O
field	O
of	O
database	O
design	O
,	O
a	O
multi-model	B-Operating_System
database	I-Operating_System
is	O
a	O
database	B-Application
management	I-Application
system	I-Application
designed	O
to	O
support	O
multiple	O
data	B-General_Concept
models	I-General_Concept
against	O
a	O
single	O
,	O
integrated	O
backend	O
.	O
</s>
<s>
In	O
contrast	O
,	O
most	O
database	B-Application
management	I-Application
systems	I-Application
are	O
organized	O
around	O
a	O
single	O
data	O
model	O
that	O
determines	O
how	O
data	O
can	O
be	O
organized	O
,	O
stored	O
,	O
and	O
manipulated	O
.	O
</s>
<s>
Document	B-General_Concept
,	O
graph	B-Application
,	O
relational	B-Application
,	O
and	O
key	B-Data_Structure
–	I-Data_Structure
value	I-Data_Structure
models	O
are	O
examples	O
of	O
data	B-General_Concept
models	I-General_Concept
that	O
may	O
be	O
supported	O
by	O
a	O
multi-model	B-Operating_System
database	I-Operating_System
.	O
</s>
<s>
The	O
relational	B-Architecture
data	I-Architecture
model	I-Architecture
became	O
popular	O
after	O
its	O
publication	O
by	O
Edgar	O
F	O
.	O
Codd	O
in	O
1970	O
.	O
</s>
<s>
Due	O
to	O
increasing	O
requirements	O
for	O
horizontal	O
scalability	O
and	O
fault	B-General_Concept
tolerance	I-General_Concept
,	O
NoSQL	B-General_Concept
databases	B-Application
became	O
prominent	O
after	O
2009	O
.	O
</s>
<s>
NoSQL	B-General_Concept
databases	B-Application
use	O
a	O
variety	O
of	O
data	B-General_Concept
models	I-General_Concept
,	O
with	O
document	B-General_Concept
,	O
graph	B-Application
,	O
and	O
key	B-Data_Structure
–	I-Data_Structure
value	I-Data_Structure
models	O
being	O
popular	O
.	O
</s>
<s>
A	O
multi-model	B-Operating_System
database	I-Operating_System
is	O
a	O
database	O
that	O
can	O
store	O
,	O
index	O
and	O
query	O
data	O
in	O
more	O
than	O
one	O
model	O
.	O
</s>
<s>
For	O
some	O
time	O
,	O
databases	B-Application
have	O
primarily	O
supported	O
only	O
one	O
model	O
,	O
such	O
as	O
:	O
relational	B-Application
database	I-Application
,	O
document-oriented	B-General_Concept
database	I-General_Concept
,	O
graph	B-Application
database	I-Application
or	O
triplestore	O
.	O
</s>
<s>
For	O
some	O
time	O
,	O
it	O
was	O
all	O
but	O
forgotten	O
(	O
or	O
considered	O
irrelevant	O
)	O
that	O
there	O
were	O
any	O
other	O
database	B-General_Concept
models	I-General_Concept
besides	O
relational	B-Application
.	O
</s>
<s>
The	O
relational	B-Architecture
model	I-Architecture
and	O
notion	O
of	O
third	O
normal	O
form	O
were	O
the	O
default	O
standard	O
for	O
all	O
data	O
storage	O
.	O
</s>
<s>
However	O
,	O
prior	O
to	O
the	O
dominance	O
of	O
relational	B-Application
data	O
modeling	O
,	O
from	O
about	O
1980	O
to	O
2005	O
,	O
the	O
hierarchical	B-General_Concept
database	I-General_Concept
model	I-General_Concept
was	O
commonly	O
used	O
.	O
</s>
<s>
Since	O
2000	O
or	O
2010	O
,	O
many	O
NoSQL	B-General_Concept
models	O
that	O
are	O
non-relational	O
,	O
including	O
documents	O
,	O
triples	O
,	O
key	B-Data_Structure
–	I-Data_Structure
value	I-Data_Structure
stores	I-Data_Structure
and	O
graphs	O
are	O
popular	O
.	O
</s>
<s>
Arguably	O
,	O
geospatial	O
data	O
,	O
temporal	O
data	O
,	O
and	O
text	O
data	O
are	O
also	O
separate	O
models	O
,	O
though	O
indexed	O
,	O
queryable	O
text	O
data	O
is	O
generally	O
termed	O
a	O
"	O
search	B-Application
engine	I-Application
"	O
rather	O
than	O
a	O
database	O
.	O
</s>
<s>
The	O
first	O
time	O
the	O
word	O
"	O
multi-model	O
"	O
has	O
been	O
associated	O
to	O
the	O
databases	B-Application
was	O
on	O
May	O
30	O
,	O
2012	O
in	O
Cologne	O
,	O
Germany	O
,	O
during	O
the	O
Luca	O
Garulli	O
's	O
key	O
note	O
"	O
NoSQL	B-General_Concept
Adoption	O
–	O
What	O
’s	O
the	O
Next	O
Step	O
?	O
"	O
.	O
</s>
<s>
Luca	O
Garulli	O
envisioned	O
the	O
evolution	O
of	O
the	O
1st	O
generation	O
NoSQL	B-General_Concept
products	O
into	O
new	O
products	O
with	O
more	O
features	O
able	O
to	O
be	O
used	O
by	O
multiple	O
use	O
cases	O
.	O
</s>
<s>
The	O
idea	O
of	O
multi-model	B-Operating_System
databases	I-Operating_System
can	O
be	O
traced	O
back	O
to	O
Object	B-General_Concept
–	I-General_Concept
Relational	I-General_Concept
Data	O
Management	O
Systems	O
(	O
ORDBMS	B-General_Concept
)	O
in	O
the	O
early	O
1990s	O
and	O
in	O
a	O
more	O
broader	O
scope	O
even	O
to	O
federated	O
and	O
integrated	O
DBMSs	O
in	O
the	O
early	O
1980s	O
.	O
</s>
<s>
An	O
ORDBMS	B-General_Concept
system	O
manages	O
different	O
types	O
of	O
data	O
such	O
as	O
relational	B-Application
,	O
object	O
,	O
text	O
and	O
spatial	O
by	O
plugging	O
domain	O
specific	O
data	O
types	O
,	O
functions	O
and	O
index	O
implementations	O
into	O
the	O
DBMS	O
kernels	O
.	O
</s>
<s>
A	O
multi-model	B-Operating_System
database	I-Operating_System
is	O
most	O
directly	O
a	O
response	O
to	O
the	O
"	O
polyglot	B-General_Concept
persistence	I-General_Concept
"	O
approach	O
of	O
knitting	O
together	O
multiple	O
database	O
products	O
,	O
each	O
handing	O
a	O
different	O
model	O
,	O
to	O
achieve	O
a	O
multi-model	O
capability	O
as	O
described	O
by	O
Martin	O
Fowler	O
.	O
</s>
<s>
This	O
strategy	O
has	O
two	O
major	O
disadvantages	O
:	O
it	O
leads	O
to	O
a	O
significant	O
increase	O
in	O
operational	O
complexity	O
,	O
and	O
there	O
is	O
no	O
support	O
for	O
maintaining	O
data	O
consistency	O
across	O
the	O
separate	O
data	O
stores	O
,	O
so	O
multi-model	B-Operating_System
databases	I-Operating_System
have	O
begun	O
to	O
fill	O
in	O
this	O
gap	O
.	O
</s>
<s>
Multi-model	B-Operating_System
databases	I-Operating_System
are	O
intended	O
to	O
offer	O
the	O
data	O
modeling	O
advantages	O
of	O
polyglot	B-General_Concept
persistence	I-General_Concept
,	O
without	O
its	O
disadvantages	O
.	O
</s>
<s>
Multi-model	B-Operating_System
databases	I-Operating_System
include	O
(	O
in	O
alphabetic	O
order	O
)	O
:	O
</s>
<s>
As	O
more	O
and	O
more	O
platforms	O
are	O
proposed	O
to	O
deal	O
with	O
multi-model	O
data	O
,	O
there	O
are	O
a	O
few	O
works	O
on	O
benchmarking	O
multi-model	B-Operating_System
databases	I-Operating_System
.	O
</s>
<s>
For	O
instance	O
,	O
Pluciennik	O
,	O
Oliveira	O
,	O
and	O
UniBench	O
reviewed	O
existing	O
multi-model	B-Operating_System
databases	I-Operating_System
and	O
made	O
an	O
evaluation	O
effort	O
towards	O
comparing	O
multi-model	B-Operating_System
databases	I-Operating_System
and	O
other	O
SQL	B-Language
and	O
NoSQL	B-General_Concept
databases	B-Application
respectively	O
.	O
</s>
<s>
They	O
pointed	O
out	O
that	O
the	O
advantages	O
of	O
multi-model	B-Operating_System
databases	I-Operating_System
over	O
single-model	O
databases	B-Application
are	O
as	O
follows	O
:	O
</s>
<s>
The	O
main	O
difference	O
between	O
the	O
available	O
multi-model	B-Operating_System
databases	I-Operating_System
is	O
related	O
to	O
their	O
architectures	O
.	O
</s>
<s>
Multi-model	B-Operating_System
databases	I-Operating_System
can	O
support	O
different	O
models	O
either	O
within	O
the	O
engine	O
or	O
via	O
different	O
layers	O
on	O
top	O
of	O
the	O
engine	O
.	O
</s>
<s>
With	O
a	O
layered	O
architecture	O
,	O
each	O
data	O
model	O
is	O
provided	O
via	O
its	O
own	O
component	B-Architecture
.	O
</s>
<s>
In	O
addition	O
to	O
offering	O
multiple	O
data	B-General_Concept
models	I-General_Concept
in	O
a	O
single	O
data	O
store	O
,	O
some	O
databases	B-Application
allow	O
developers	O
to	O
easily	O
define	O
custom	O
data	B-General_Concept
models	I-General_Concept
.	O
</s>
<s>
JSON	O
documents	O
,	O
graphs	O
,	O
and	O
relational	B-Application
tables	O
can	O
all	O
be	O
implemented	O
in	O
a	O
manner	O
that	O
inherits	O
the	O
horizontal	O
scalability	O
and	O
fault-tolerance	B-General_Concept
of	O
the	O
underlying	O
data	O
store	O
.	O
</s>
