<s>
The	O
Unique	B-Language
Particle	I-Language
Attribution	I-Language
(	O
UPA	O
)	O
rule	O
is	O
a	O
mechanism	O
to	O
prevent	O
ambiguity	O
in	O
W3C	O
XML	B-Protocol
Schema	O
version	O
1.0	O
.	O
</s>
<s>
Due	O
to	O
the	O
UPA	O
rule	O
the	O
XML	B-Protocol
schema	O
fragment	O
given	O
below	O
is	O
prohibited	O
:	O
</s>
<s>
Given	O
the	O
XML	B-Protocol
instance	O
fragment	O
:	O
</s>
<s>
This	O
ambiguity	O
violates	O
the	O
UPA	O
rule	O
and	O
the	O
corresponding	O
XML	B-Protocol
schema	O
therefore	O
needs	O
to	O
be	O
rejected	O
by	O
XML	B-Protocol
schema	O
processors	O
compliant	O
to	O
W3C	O
XML	B-Protocol
Schema	O
version	O
1.0	O
.	O
</s>
<s>
This	O
particular	O
example	O
no	O
longer	O
violates	O
the	O
Unique	O
Particle	O
Attribute	O
constraint	O
in	O
XML	B-Protocol
Schema	O
version	O
1.1	O
,	O
which	O
disambiguates	O
it	O
by	O
saying	O
that	O
when	O
an	O
element	O
matches	O
both	O
an	O
element	O
particle	O
and	O
a	O
wildcard	O
,	O
the	O
element	O
particle	O
wins	O
.	O
</s>
