<s>
XML	B-Language
validation	I-Language
is	O
the	O
process	O
of	O
checking	O
a	O
document	O
written	O
in	O
XML	B-Protocol
(	O
eXtensible	B-Protocol
Markup	I-Protocol
Language	I-Protocol
)	O
to	O
confirm	O
that	O
it	O
is	O
both	O
well-formed	B-Language
and	O
also	O
"	O
valid	O
"	O
in	O
that	O
it	O
follows	O
a	O
defined	O
structure	O
.	O
</s>
<s>
A	O
well-formed	B-Language
document	I-Language
follows	O
the	O
basic	O
syntactic	O
rules	O
of	O
XML	B-Protocol
,	O
which	O
are	O
the	O
same	O
for	O
all	O
XML	B-Protocol
documents	I-Protocol
.	O
</s>
<s>
A	O
valid	O
document	O
also	O
respects	O
the	O
rules	O
dictated	O
by	O
a	O
particular	O
DTD	B-Language
or	O
XML	B-Protocol
schema	O
.	O
</s>
<s>
Automated	O
tools	O
–	O
validators	B-Application
–	O
can	O
perform	O
well-formedness	O
tests	O
and	O
many	O
other	O
validation	O
tests	O
,	O
but	O
not	O
those	O
that	O
require	O
human	O
judgement	O
,	O
such	O
as	O
correct	O
application	O
of	O
a	O
schema	O
to	O
a	O
data	O
set	O
.	O
</s>
<s>
Schematron	B-Language
,	O
a	O
method	O
for	O
advanced	O
XML	B-Language
validation	I-Language
.	O
</s>
<s>
xmllint	B-Application
is	O
a	O
command	O
line	O
XML	B-Protocol
tool	O
that	O
can	O
perform	O
XML	B-Language
validation	I-Language
.	O
</s>
<s>
It	O
can	O
be	O
found	O
in	O
UNIX	B-Application
/	O
Linux	B-Application
environments	O
.	O
</s>
<s>
XML	B-Protocol
toolkit	O
.	O
</s>
<s>
Validate	O
your	O
XML	B-Protocol
data	O
.	O
</s>
<s>
Validate	O
XML	B-Protocol
files	O
against	O
an	O
XML	B-Protocol
Schema	O
.	O
</s>
