<s>
An	O
XML	B-Application
database	I-Application
is	O
a	O
data	B-Application
persistence	I-Application
software	O
system	O
that	O
allows	O
data	O
to	O
be	O
specified	O
,	O
and	O
sometimes	O
stored	O
,	O
in	O
XML	B-Protocol
format	O
.	O
</s>
<s>
This	O
data	O
can	O
be	O
queried	B-Language
,	O
transformed	O
,	O
exported	O
and	O
returned	O
to	O
a	O
calling	O
system	O
.	O
</s>
<s>
XML	B-Application
databases	I-Application
are	O
a	O
flavor	O
of	O
document-oriented	B-General_Concept
databases	I-General_Concept
which	O
are	O
in	O
turn	O
a	O
category	O
of	O
NoSQL	B-General_Concept
database	O
.	O
</s>
<s>
There	O
are	O
a	O
number	O
of	O
reasons	O
to	O
directly	O
specify	O
data	O
in	O
XML	B-Protocol
or	O
other	O
document	O
formats	O
such	O
as	O
JSON	B-General_Concept
.	O
</s>
<s>
For	O
XML	B-Protocol
in	O
particular	O
,	O
they	O
include	O
:	O
</s>
<s>
Steve	O
O'Connell	O
gives	O
one	O
reason	O
for	O
the	O
use	O
of	O
XML	B-Protocol
in	O
databases	O
:	O
the	O
increasingly	O
common	O
use	O
of	O
XML	B-Protocol
for	O
data	B-Architecture
transport	I-Architecture
,	O
which	O
has	O
meant	O
that	O
"	O
data	O
is	O
extracted	O
from	O
databases	O
and	O
put	O
into	O
XML	B-Protocol
documents	I-Protocol
and	O
vice-versa	O
"	O
.	O
</s>
<s>
It	O
may	O
prove	O
more	O
efficient	O
(	O
in	O
terms	O
of	O
conversion	O
costs	O
)	O
and	O
easier	O
to	O
store	O
the	O
data	O
in	O
XML	B-Protocol
format	O
.	O
</s>
<s>
In	O
content-based	O
applications	O
,	O
the	O
ability	O
of	O
the	O
native	O
XML	B-Application
database	I-Application
also	O
minimizes	O
the	O
need	O
for	O
extraction	O
or	O
entry	O
of	O
metadata	O
to	O
support	O
searching	O
and	O
navigation	O
.	O
</s>
<s>
XML-enabled	O
databases	O
typically	O
offer	O
one	O
or	O
more	O
of	O
the	O
following	O
approaches	O
to	O
storing	O
XML	B-Protocol
within	O
the	O
traditional	O
relational	O
structure	O
:	O
</s>
<s>
RDBMS	O
that	O
support	O
the	O
ISO	O
XML	B-Protocol
Type	O
are	O
:	O
</s>
<s>
Typically	O
an	O
XML-enabled	O
database	O
is	O
best	O
suited	O
where	O
the	O
majority	O
of	O
data	O
are	O
non-XML	O
.	O
</s>
<s>
For	O
datasets	O
where	O
the	O
majority	O
of	O
data	O
are	O
XML	B-Protocol
,	O
a	O
native	O
XML	B-Application
database	I-Application
is	O
better	O
suited	O
.	O
</s>
<s>
Native	O
XML	B-Application
databases	I-Application
are	O
especially	O
tailored	O
for	O
working	O
with	O
XML	B-Protocol
data	O
.	O
</s>
<s>
As	O
managing	O
XML	B-Protocol
as	O
large	O
strings	O
would	O
be	O
inefficient	O
,	O
and	O
due	O
to	O
the	O
hierarchical	O
nature	O
of	O
XML	B-Protocol
,	O
custom	O
optimized	O
data	O
structures	O
are	O
used	O
for	O
storage	O
and	O
querying	O
.	O
</s>
<s>
XML	B-Protocol
nodes	O
and	O
documents	O
are	O
the	O
fundamental	O
unit	O
of	O
(	O
logical	O
)	O
storage	O
,	O
just	O
as	O
a	O
relational	B-Application
database	I-Application
has	O
fields	O
and	O
rows	O
.	O
</s>
<s>
The	O
standard	O
for	O
querying	O
XML	B-Protocol
data	O
per	O
W3C	O
recommendation	O
is	O
XQuery	B-Language
;	O
the	O
latest	O
version	O
is	O
XQuery	B-Language
3.1	O
.	O
</s>
<s>
XQuery	B-Language
includes	O
XPath	B-Language
as	O
a	O
sub-language	O
and	O
XML	B-Protocol
itself	O
is	O
a	O
valid	O
sub-syntax	O
of	O
XQuery	B-Language
.	O
</s>
<s>
In	O
addition	O
to	O
XPath	B-Language
,	O
some	O
XML	B-Application
databases	I-Application
support	O
XSLT	B-Application
as	O
a	O
method	O
of	O
transforming	O
documents	O
or	O
query	O
results	O
retrieved	O
from	O
the	O
database	O
.	O
</s>
<s>
For	O
data-centric	O
XML	B-Protocol
datasets	O
,	O
the	O
unique	O
and	O
distinct	O
keyword	O
search	O
method	O
,	O
namely	O
,	O
XDMA	O
for	O
XML	B-Application
databases	I-Application
is	O
designed	O
and	O
developed	O
based	O
on	O
dual	O
indexing	O
and	O
mutual	O
summation	O
.	O
</s>
