<s>
Semi-structured	B-Application
data	I-Application
is	O
a	O
form	O
of	O
structured	B-Application
data	I-Application
that	O
does	O
not	O
obey	O
the	O
tabular	O
structure	O
of	O
data	B-Application
models	I-Application
associated	O
with	O
relational	B-Application
databases	I-Application
or	O
other	O
forms	O
of	O
data	B-Application
tables	I-Application
,	O
but	O
nonetheless	O
contains	O
tags	B-General_Concept
or	O
other	O
markers	O
to	O
separate	O
semantic	O
elements	O
and	O
enforce	O
hierarchies	O
of	O
records	O
and	O
fields	O
within	O
the	O
data	O
.	O
</s>
<s>
In	O
semi-structured	B-Application
data	I-Application
,	O
the	O
entities	O
belonging	O
to	O
the	O
same	O
class	O
may	O
have	O
different	O
attributes	O
even	O
though	O
they	O
are	O
grouped	O
together	O
,	O
and	O
the	O
attributes	O
 '	O
order	O
is	O
not	O
important	O
.	O
</s>
<s>
Semi-structured	B-Application
data	I-Application
are	O
increasingly	O
occurring	O
since	O
the	O
advent	O
of	O
the	O
Internet	O
where	O
full-text	B-Application
documents	O
and	O
databases	B-Application
are	O
not	O
the	O
only	O
forms	O
of	O
data	O
anymore	O
,	O
and	O
different	O
applications	O
need	O
a	O
medium	O
for	O
exchanging	O
information	O
.	O
</s>
<s>
In	O
object-oriented	B-Application
databases	I-Application
,	O
one	O
often	O
finds	O
semi-structured	B-Application
data	I-Application
.	O
</s>
<s>
XML	B-Protocol
,	O
other	O
markup	O
languages	O
,	O
email	O
,	O
and	O
EDI	O
are	O
all	O
forms	O
of	O
semi-structured	B-Application
data	I-Application
.	O
</s>
<s>
OEM	B-Application
(	O
Object	B-Application
Exchange	I-Application
Model	I-Application
)	O
was	O
created	O
prior	O
to	O
XML	B-Protocol
as	O
a	O
means	O
of	O
self-describing	O
a	O
data	O
structure	O
.	O
</s>
<s>
XML	B-Protocol
has	O
been	O
popularized	O
by	O
web	O
services	O
that	O
are	O
developed	O
utilizing	O
SOAP	B-Application
principles	O
.	O
</s>
<s>
Some	O
types	O
of	O
data	O
described	O
here	O
as	O
"	O
semi-structured	O
"	O
,	O
especially	O
XML	B-Protocol
,	O
suffer	O
from	O
the	O
impression	O
that	O
they	O
are	O
incapable	O
of	O
structural	O
rigor	O
at	O
the	O
same	O
functional	O
level	O
as	O
Relational	O
Tables	O
and	O
Rows	O
.	O
</s>
<s>
Indeed	O
,	O
the	O
view	O
of	O
XML	B-Protocol
as	O
inherently	O
semi-structured	O
(	O
previously	O
,	O
it	O
was	O
referred	O
to	O
as	O
"	O
unstructured	O
"	O
)	O
has	O
handicapped	O
its	O
use	O
for	O
a	O
widening	O
range	O
of	O
data-centric	O
applications	O
.	O
</s>
<s>
Even	O
documents	O
,	O
normally	O
thought	O
of	O
as	O
the	O
epitome	O
of	O
semi-structure	O
,	O
can	O
be	O
designed	O
with	O
virtually	O
the	O
same	O
rigor	O
as	O
database	B-Application
schema	I-Application
,	O
enforced	O
by	O
the	O
XML	B-Language
schema	I-Language
and	O
processed	O
by	O
both	O
commercial	O
and	O
custom	O
software	O
programs	O
without	O
reducing	O
their	O
usability	O
by	O
human	O
readers	O
.	O
</s>
<s>
In	O
view	O
of	O
this	O
fact	O
,	O
XML	B-Protocol
might	O
be	O
referred	O
to	O
as	O
having	O
"	O
flexible	O
structure	O
"	O
capable	O
of	O
human-centric	O
flow	O
and	O
hierarchy	O
as	O
well	O
as	O
highly	O
rigorous	O
element	O
structure	O
and	O
data	O
typing	O
.	O
</s>
<s>
The	O
concept	O
of	O
XML	B-Protocol
as	O
"	O
human-readable	O
"	O
,	O
however	O
,	O
can	O
only	O
be	O
taken	O
so	O
far	O
.	O
</s>
<s>
Some	O
implementations/dialects	O
of	O
XML	B-Protocol
,	O
such	O
as	O
the	O
XML	B-Protocol
representation	O
of	O
the	O
contents	O
of	O
a	O
Microsoft	O
Word	O
document	O
,	O
as	O
implemented	O
in	O
Office	O
2007	O
and	O
later	O
versions	O
,	O
utilize	O
dozens	O
or	O
even	O
hundreds	O
of	O
different	O
kinds	O
of	O
tags	B-General_Concept
that	O
reflect	O
a	O
particular	O
problem	O
domain	O
-	O
in	O
Word	O
's	O
case	O
,	O
formatting	O
at	O
the	O
character	O
and	O
paragraph	O
and	O
document	O
level	O
,	O
definitions	O
of	O
styles	O
,	O
inclusion	O
of	O
citations	O
,	O
etc	O
.	O
</s>
<s>
Understanding	O
even	O
a	O
portion	O
of	O
such	O
an	O
XML	B-Protocol
document	I-Protocol
by	O
reading	O
it	O
,	O
let	O
alone	O
catching	O
errors	O
in	O
its	O
structure	O
,	O
is	O
impossible	O
without	O
a	O
very	O
deep	O
prior	O
understanding	O
of	O
the	O
specific	O
XML	B-Protocol
implementation	O
,	O
along	O
with	O
assistance	O
by	O
software	O
that	O
understands	O
the	O
XML	B-Language
schema	I-Language
that	O
has	O
been	O
employed	O
.	O
</s>
<s>
Such	O
text	O
is	O
not	O
"	O
human-understandable	O
"	O
any	O
more	O
than	O
a	O
book	O
written	O
in	O
Swahili	O
(	O
which	O
uses	O
the	O
Latin	O
alphabet	O
)	O
would	O
be	O
to	O
an	O
American	O
or	O
Western	O
European	O
who	O
does	O
not	O
know	O
a	O
word	O
of	O
that	O
language	O
:	O
the	O
tags	B-General_Concept
are	O
symbols	O
that	O
are	O
meaningless	O
to	O
a	O
person	O
unfamiliar	O
with	O
the	O
domain	O
.	O
</s>
<s>
JSON	B-General_Concept
or	O
JavaScript	B-General_Concept
Object	I-General_Concept
Notation	I-General_Concept
,	O
is	O
an	O
open	O
standard	O
format	O
that	O
uses	O
human-readable	O
text	O
to	O
transmit	O
data	O
objects	O
consisting	O
of	O
attribute	O
–	O
value	O
pairs	O
.	O
</s>
<s>
It	O
is	O
used	O
primarily	O
to	O
transmit	O
data	O
between	O
a	O
server	O
and	O
web	O
application	O
,	O
as	O
an	O
alternative	O
to	O
XML	B-Protocol
.	O
</s>
<s>
JSON	B-General_Concept
has	O
been	O
popularized	O
by	O
web	O
services	O
developed	O
utilizing	O
REST	O
principles	O
.	O
</s>
<s>
There	O
is	O
a	O
new	O
breed	O
of	O
databases	B-Application
such	O
as	O
MongoDB	B-Application
and	O
Couchbase	B-Operating_System
that	O
store	O
data	O
natively	O
in	O
JSON	B-General_Concept
format	O
,	O
leveraging	O
the	O
pros	O
of	O
semi-structured	B-Application
data	I-Application
architecture	O
.	O
</s>
<s>
Programmers	O
persisting	O
objects	O
from	O
their	O
application	O
to	O
a	O
database	O
do	O
not	O
need	O
to	O
worry	O
about	O
object-relational	B-Architecture
impedance	I-Architecture
mismatch	I-Architecture
,	O
but	O
can	O
often	O
serialize	O
objects	O
via	O
a	O
light-weight	O
library	O
.	O
</s>
<s>
Support	O
for	O
nested	O
or	O
hierarchical	O
data	O
often	O
simplifies	O
data	B-Application
models	I-Application
representing	O
complex	O
relationships	O
between	O
entities	O
.	O
</s>
<s>
Support	O
for	O
lists	O
of	O
objects	O
simplifies	O
data	B-Application
models	I-Application
by	O
avoiding	O
messy	O
translations	O
of	O
lists	O
into	O
a	O
relational	O
data	B-Application
model	I-Application
.	O
</s>
<s>
The	O
traditional	O
relational	O
data	B-Application
model	I-Application
has	O
a	O
popular	O
and	O
ready-made	O
query	O
language	O
,	O
SQL	B-Language
.	O
</s>
<s>
Prone	O
to	O
"	O
garbage	O
in	O
,	O
garbage	O
out	O
"	O
;	O
by	O
removing	O
restraints	O
from	O
the	O
data	B-Application
model	I-Application
,	O
there	O
is	O
less	O
fore-thought	O
that	O
is	O
necessary	O
to	O
operate	O
a	O
data	O
application	O
.	O
</s>
