<s>
OML	B-General_Concept
(	O
Outline	O
Markup	O
Language	O
)	O
is	O
an	O
XML	B-Protocol
format	O
for	O
outlines	O
.	O
</s>
<s>
The	O
specification	O
is	O
designed	O
to	O
build	O
upon	O
the	O
concepts	O
found	O
in	O
OPML	B-Application
,	O
with	O
the	O
goal	O
of	O
fixing	O
some	O
of	O
its	O
limitations	O
.	O
</s>
<s>
OML	B-General_Concept
has	O
a	O
structure	O
similar	O
to	O
OPML	B-Application
.	O
</s>
<s>
Its	O
advocates	O
claim	O
that	O
although	O
it	O
is	O
as	O
simple	O
and	O
as	O
flexible	O
as	O
OPML	B-Application
,	O
its	O
extension	O
mechanism	O
is	O
better	O
than	O
that	O
of	O
OPML	B-Application
.	O
</s>
<s>
Instead	O
of	O
letting	O
users	O
add	O
attributes	O
freely	O
,	O
OML	B-General_Concept
introduces	O
an	O
<item> element (child element of <outline> ) ; instances of the <item>	O
element	O
may	O
be	O
added	O
freely	O
.	O
</s>
<s>
The	O
resulting	O
documents	O
are	O
claimed	O
to	O
be	O
easier	O
to	O
parse	O
than	O
equivalent	O
OPML	B-Application
documents	O
.	O
</s>
<s>
Readers	O
of	O
OPML	B-Application
never	O
know	O
what	O
attributes	O
others	O
may	O
have	O
added	O
to	O
standard	O
elements	O
;	O
so	O
an	O
element	O
the	O
reader	O
wants	O
to	O
parse	O
may	O
contain	O
a	O
mixture	O
of	O
known	O
and	O
unknown	O
attributes	O
.	O
</s>
<s>
This	O
claimed	O
disadvantage	O
of	O
OPML	B-Application
actually	O
applies	O
to	O
any	O
XML-based	O
format	O
,	O
including	O
OML	B-General_Concept
,	O
because	O
XML	B-Language
namespaces	I-Language
may	O
add	O
attributes	O
to	O
existing	O
tags	O
;	O
however	O
,	O
OPML	B-Application
is	O
unusual	O
in	O
its	O
enthusiasm	O
for	O
free-form	O
definition	O
of	O
new	O
attributes	O
.	O
</s>
<s>
In	O
OML	B-General_Concept
,	O
extensions	O
are	O
added	O
in	O
the	O
form	O
of	O
<item>s instead; an unknown <item>	O
may	O
be	O
discarded	O
without	O
harming	O
known	O
data	O
elsewhere	O
in	O
the	O
file	O
.	O
</s>
<s>
The	O
approach	O
taken	O
by	O
OML	B-General_Concept
is	O
designed	O
to	O
be	O
more	O
in	O
keeping	O
with	O
the	O
approach	O
of	O
other	O
XML-based	O
languages	O
and	O
with	O
the	O
philosophy	O
of	O
some	O
standards	O
organizations	O
.	O
</s>
<s>
Despite	O
its	O
claimed	O
advantages	O
,	O
OML	B-General_Concept
has	O
not	O
seen	O
wide	O
use	O
.	O
</s>
<s>
Reasons	O
for	O
the	O
greater	O
popularity	O
of	O
OPML	B-Application
may	O
include	O
the	O
relative	O
newness	O
of	O
OML	B-General_Concept
(	O
finalized	O
in	O
May	O
2003	O
)	O
,	O
and	O
non-technical	O
political	O
issues	O
between	O
members	O
of	O
the	O
XML	B-Protocol
community	O
.	O
</s>
<s>
Critics	O
of	O
OML	B-General_Concept
point	O
out	O
OML	B-General_Concept
does	O
n't	O
have	O
a	O
mechanism	O
to	O
preserve	O
whitespace	O
.	O
</s>
