<s>
The	O
semi-structured	B-General_Concept
model	I-General_Concept
is	O
a	O
database	B-General_Concept
model	I-General_Concept
where	O
there	O
is	O
no	O
separation	O
between	O
the	O
data	B-General_Concept
and	O
the	O
schema	B-Application
,	O
and	O
the	O
amount	O
of	O
structure	O
used	O
depends	O
on	O
the	O
purpose	O
.	O
</s>
<s>
It	O
can	O
represent	O
the	O
information	O
of	O
some	O
data	B-General_Concept
sources	O
that	O
cannot	O
be	O
constrained	O
by	O
schema	B-Application
.	O
</s>
<s>
It	O
provides	O
a	O
flexible	O
format	O
for	O
data	B-General_Concept
exchange	O
between	O
different	O
types	O
of	O
databases	O
.	O
</s>
<s>
It	O
can	O
be	O
helpful	O
to	O
view	O
structured	O
data	B-General_Concept
as	O
semi-structured	O
(	O
for	O
browsing	O
purposes	O
)	O
.	O
</s>
<s>
The	O
schema	B-Application
can	O
easily	O
be	O
changed	O
.	O
</s>
<s>
The	O
data	B-General_Concept
transfer	O
format	O
may	O
be	O
portable	O
.	O
</s>
<s>
The	O
primary	O
trade-off	O
being	O
made	O
in	O
using	O
a	O
semi-structured	O
database	B-General_Concept
model	I-General_Concept
is	O
that	O
queries	O
cannot	O
be	O
made	O
as	O
efficiently	O
as	O
in	O
a	O
more	O
constrained	O
structure	O
,	O
such	O
as	O
in	O
the	O
relational	B-Architecture
model	I-Architecture
.	O
</s>
<s>
This	O
makes	O
navigational	O
or	O
path-based	O
queries	O
quite	O
efficient	O
,	O
but	O
for	O
doing	O
searches	O
over	O
many	O
records	O
(	O
as	O
is	O
typical	O
in	O
SQL	B-Language
)	O
,	O
it	O
is	O
not	O
as	O
efficient	O
because	O
it	O
has	O
to	O
seek	O
around	O
the	O
disk	O
following	O
pointers	O
.	O
</s>
<s>
The	O
Object	B-Application
Exchange	I-Application
Model	I-Application
(	O
OEM	O
)	O
is	O
one	O
standard	O
to	O
express	O
semi-structured	B-Application
data	I-Application
,	O
another	O
way	O
is	O
XML	B-Protocol
.	O
</s>
