<s>
Semantic	B-Application
file	I-Application
systems	I-Application
are	O
file	B-Application
systems	I-Application
used	O
for	O
information	O
persistence	O
which	O
structure	O
the	O
data	O
according	O
to	O
their	O
semantics	B-Application
and	O
intent	O
,	O
rather	O
than	O
the	O
location	O
as	O
with	O
current	O
file	B-Application
systems	I-Application
.	O
</s>
<s>
Traditional	O
hierarchical	O
file-systems	B-Application
tend	O
to	O
impose	O
a	O
burden	O
,	O
for	O
example	O
when	O
a	O
sub-directory	O
layout	O
is	O
contradicting	O
a	O
user	O
's	O
perception	O
of	O
where	O
files	O
would	O
be	O
stored	O
.	O
</s>
<s>
Semantic	B-Application
file	I-Application
systems	I-Application
raise	O
technical	O
design	O
challenges	O
as	O
indexes	O
of	O
words	O
,	O
tags	O
or	O
elementary	O
signs	O
of	O
some	O
sort	O
have	O
to	O
be	O
created	O
and	O
constantly	O
updated	O
,	O
maintained	O
and	O
cached	O
for	O
performance	O
to	O
offer	O
the	O
desired	O
random	O
,	O
multi-variate	O
access	O
to	O
files	O
in	O
addition	O
to	O
the	O
underlying	O
,	O
mostly	O
traditional	O
block-based	O
filesystem	B-Application
.	O
</s>
