<s>
The	O
term	O
round-trip	O
is	O
used	O
in	O
document	B-General_Concept
conversion	I-General_Concept
particularly	O
involving	O
markup	O
languages	O
such	O
as	O
XML	B-Protocol
and	O
SGML	B-Language
.	O
</s>
<s>
More	O
generally	O
it	O
means	O
converting	O
from	O
any	O
data	O
representation	O
and	O
back	O
again	O
,	O
including	O
from	O
one	O
data	B-General_Concept
structure	I-General_Concept
to	O
another	O
.	O
</s>
<s>
For	O
example	O
,	O
suppose	O
an	O
HTML	B-Language
document	O
is	O
saved	O
as	O
plain	O
text	O
( *	O
.txt	O
)	O
.	O
</s>
<s>
If	O
a	O
lossless	B-Algorithm
file	I-Algorithm
,	O
such	O
as	O
a	O
BMP	B-Device
or	O
PNG	O
file	O
,	O
is	O
converted	O
to	O
JPEG	O
and	O
back	O
again	O
then	O
the	O
result	O
will	O
be	O
different	O
from	O
the	O
original	O
(	O
although	O
it	O
may	O
be	O
visually	O
very	O
similar	O
)	O
.	O
</s>
<s>
Markup	O
languages	O
such	O
as	O
XML	B-Protocol
can	O
,	O
in	O
principle	O
,	O
hold	O
any	O
information	O
and	O
so	O
the	O
process	O
docA	O
→	O
docX	O
→	O
docA	O
 '	O
could	O
be	O
designed	O
to	O
avoid	O
information	O
loss	O
.	O
</s>
<s>
It	O
is	O
now	O
common	O
to	O
convert	O
legacy	O
formats	O
to	O
XML	B-Protocol
formats	O
because	O
they	O
have	O
greater	O
interoperability	O
and	O
a	O
wider	O
set	O
of	O
available	O
tools	O
.	O
</s>
<s>
Thus	O
it	O
is	O
possible	O
to	O
convert	O
Word	O
documents	O
to	O
an	O
XML	B-Protocol
format	O
and	O
reimport	O
them	O
.	O
</s>
<s>
The	O
XML	B-Protocol
document	I-Protocol
should	O
contain	O
identical	O
information	O
to	O
the	O
legacy	O
format	O
.	O
</s>
<s>
An	O
important	O
condition	O
is	O
that	O
the	O
roundtrip	O
(	O
legacy	O
→	O
XML	B-Protocol
→	O
legacy	O
 '	O
)	O
should	O
result	O
in	O
effectively	O
identical	O
documents	O
.	O
</s>
<s>
While	O
this	O
may	O
be	O
needed	O
for	O
some	O
cases	O
,	O
the	O
idea	O
of	O
a	O
round-trip	O
conversion	O
is	O
to	O
go	O
through	O
another	O
format	O
representation	O
or	O
data	B-General_Concept
structure	I-General_Concept
and	O
back	O
again	O
.	O
</s>
