<s>
A	O
system	B-Language
identifier	I-Language
is	O
a	O
document-processing	O
construct	O
introduced	O
in	O
the	O
HyTime	B-Language
markup	O
language	O
as	O
a	O
supplement	O
to	O
SGML	B-Language
.	O
</s>
<s>
It	O
was	O
subsequently	O
incorporated	O
into	O
the	O
HTML	B-Language
and	O
XML	B-Protocol
markup	O
languages	O
.	O
</s>
<s>
In	O
HyTime	B-Language
,	O
there	O
are	O
two	O
kinds	O
of	O
system	B-Language
identifier	I-Language
:	O
formal	O
system	B-Language
identifier	I-Language
(	O
FSI	O
)	O
and	O
simple	O
system	B-Language
identifier	I-Language
.	O
</s>
<s>
In	O
HTML	B-Language
and	O
XML	B-Protocol
,	O
a	O
system	B-Language
identifier	I-Language
is	O
a	O
fragmentless	O
URI	B-Protocol
reference	I-Protocol
.	O
</s>
<s>
In	O
the	O
following	O
example	O
,	O
the	O
system	B-Language
identifier	I-Language
is	O
the	O
text	O
contained	O
within	O
quotes	O
:	O
</s>
