<s>
The	O
XQuery	B-Application
and	I-Application
XPath	I-Application
Data	I-Application
Model	I-Application
(	O
XDM	O
)	O
is	O
the	O
data	B-Application
model	I-Application
shared	O
by	O
the	O
XPath	B-Language
2.0	O
,	O
XSLT	B-Application
2.0	I-Application
,	O
XQuery	B-Language
,	O
and	O
XForms	B-Application
programming	O
languages	O
.	O
</s>
<s>
Originally	O
,	O
it	O
was	O
based	O
on	O
the	O
XPath	B-Language
1.0	I-Language
data	B-Application
model	I-Application
which	O
in	O
turn	O
is	O
based	O
on	O
the	O
XML	B-Protocol
Information	O
Set	O
.	O
</s>
<s>
The	O
XDM	O
consists	O
of	O
flat	O
sequences	O
of	O
zero	O
or	O
more	O
items	O
which	O
can	O
be	O
typed	O
or	O
untyped	O
,	O
and	O
are	O
either	O
atomic	O
values	O
or	O
XML	B-Protocol
nodes	O
(	O
of	O
seven	O
kinds	O
:	O
document	O
,	O
element	O
,	O
attribute	O
,	O
text	O
,	O
namespace	O
,	O
processing	O
instruction	O
,	O
and	O
comment	O
)	O
.	O
</s>
<s>
Instances	O
of	O
the	O
XDM	O
can	O
optionally	O
be	O
XML	B-Protocol
schema-validated	O
.	O
</s>
