<s>
Tagsistant	B-Application
is	O
a	O
semantic	B-Application
file	I-Application
system	I-Application
for	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
,	O
written	O
in	O
C	B-Language
and	O
based	O
on	O
FUSE	B-Application
.	O
</s>
<s>
Unlike	O
traditional	O
file	B-Application
systems	I-Application
that	O
use	O
hierarchies	O
of	O
directories	B-Application
to	O
locate	O
objects	O
,	O
Tagsistant	B-Application
introduces	O
the	O
concept	O
of	O
tags	B-General_Concept
.	O
</s>
<s>
In	O
computing	O
,	O
a	O
file	B-Application
system	I-Application
is	O
a	O
type	O
of	O
data	O
store	O
which	O
could	O
be	O
used	O
to	O
store	O
,	O
retrieve	O
and	O
update	O
files	B-Operating_System
.	O
</s>
<s>
Each	O
file	O
can	O
be	O
uniquely	O
located	O
by	O
its	O
path	B-Application
.	O
</s>
<s>
The	O
user	O
must	O
know	O
the	O
path	B-Application
in	O
advance	O
to	O
access	O
a	O
file	O
and	O
the	O
path	B-Application
does	O
not	O
necessarily	O
include	O
any	O
information	O
about	O
the	O
content	O
of	O
the	O
file	O
.	O
</s>
<s>
Tagsistant	B-Application
uses	O
a	O
complementary	O
approach	O
based	O
on	O
tags	B-General_Concept
.	O
</s>
<s>
The	O
user	O
can	O
create	O
a	O
set	O
of	O
tags	B-General_Concept
and	O
apply	O
those	O
tags	B-General_Concept
to	O
files	B-Operating_System
,	O
directories	B-Application
and	O
other	O
objects	O
(	O
devices	B-Application
,	O
pipes	B-Operating_System
,	O
...	O
)	O
.	O
</s>
<s>
The	O
user	O
can	O
then	O
search	O
all	O
the	O
objects	O
that	O
match	O
a	O
subset	O
of	O
tags	B-General_Concept
,	O
called	O
a	O
query	O
.	O
</s>
<s>
This	O
kind	O
of	O
approach	O
is	O
well	O
suited	O
for	O
managing	O
user	O
contents	O
like	O
pictures	O
,	O
audio	O
recordings	O
,	O
movies	O
and	O
text	O
documents	O
but	O
is	O
incompatible	O
with	O
system	O
files	B-Operating_System
(	O
like	O
libraries	O
,	O
commands	O
and	O
configurations	O
)	O
where	O
the	O
univocity	O
of	O
the	O
path	B-Application
is	O
a	O
security	O
requirement	O
to	O
prevent	O
the	O
access	O
to	O
a	O
wrong	O
content	O
.	O
</s>
<s>
A	O
Tagsistant	B-Application
file	B-Application
system	I-Application
features	O
four	O
main	O
directories	B-Application
:	O
</s>
<s>
Tags	B-General_Concept
are	O
created	O
as	O
sub	O
directories	B-Application
of	O
the	O
tags/	O
directory	B-Application
and	O
can	O
be	O
used	O
in	O
queries	O
complying	O
to	O
this	O
syntax	O
:	O
</s>
<s>
where	O
a	O
subquery	O
is	O
an	O
unlimited	O
list	O
of	O
tags	B-General_Concept
,	O
concatenated	O
as	O
directories	B-Application
:	O
</s>
<s>
The	O
portion	O
of	O
a	O
path	B-Application
delimited	O
by	O
tags/	O
and	O
@	O
/	O
is	O
the	O
actual	O
query	O
.	O
</s>
<s>
The	O
query	O
syntax	O
deliberately	O
violates	O
the	O
POSIX	O
file	B-Application
system	I-Application
semantics	O
by	O
allowing	O
a	O
path	B-Application
token	O
to	O
be	O
a	O
descendant	O
of	O
itself	O
,	O
like	O
in	O
tags/t1/t2/	O
+	O
/t1/t4/	O
@	O
where	O
t1/	O
appears	O
twice	O
.	O
</s>
<s>
As	O
a	O
consequence	O
a	O
recursive	O
scan	O
of	O
a	O
Tagsistant	B-Application
file	B-Application
system	I-Application
will	O
exit	O
with	O
an	O
error	O
or	O
endlessly	O
loop	O
,	O
as	O
done	O
by	O
UNIX	B-Application
find	B-Application
:	O
</s>
<s>
This	O
drawback	O
is	O
balanced	O
by	O
the	O
possibility	O
to	O
list	O
the	O
tags	B-General_Concept
inside	O
a	O
query	O
in	O
any	O
order	O
.	O
</s>
<s>
The	O
query	O
tags/t1/t2/	O
@	O
/	O
is	O
completely	O
equivalent	O
to	O
tags/t2/t1/	O
@	O
/	O
and	O
tags/t1/	O
+	O
/t2/t3/	O
@	O
/	O
is	O
equivalent	O
to	O
tags/t2/t3/	O
+	O
/t1/	O
@	O
/	O
.	O
</s>
<s>
The	O
@	O
/	O
element	O
has	O
the	O
precise	O
purpose	O
of	O
restoring	O
the	O
POSIX	O
semantics	O
:	O
the	O
path	B-Application
tags/t1/	O
@	O
/directory/	O
refers	O
to	O
a	O
traditional	O
directory	B-Application
and	O
a	O
recursive	O
scan	O
of	O
this	O
path	B-Application
will	O
properly	O
perform	O
.	O
</s>
<s>
Tagsistant	B-Application
features	O
a	O
simple	O
reasoner	O
which	O
expands	O
the	O
results	O
of	O
a	O
query	O
by	O
including	O
objects	O
tagged	O
with	O
related	O
tags	B-General_Concept
.	O
</s>
<s>
A	O
relation	O
between	O
two	O
tags	B-General_Concept
can	O
be	O
established	O
inside	O
the	O
relations/	O
directory	B-Application
following	O
a	O
three	O
level	O
pattern	O
:	O
</s>
<s>
To	O
include	O
the	O
rock	O
tag	B-General_Concept
in	O
the	O
music	O
tag	B-General_Concept
,	O
the	O
UNIX	B-Application
command	O
mkdir	O
can	O
be	O
used	O
:	O
</s>
<s>
The	O
web	O
of	O
relations	O
created	O
inside	O
the	O
relations/	O
directory	B-Application
constitutes	O
a	O
basic	O
form	O
of	O
ontology	O
.	O
</s>
<s>
Tagsistant	B-Application
features	O
an	O
autotagging	O
plugin	O
stack	O
which	O
gets	O
called	O
when	O
a	O
file	O
or	O
a	O
symlink	O
is	O
written	O
.	O
</s>
<s>
The	O
list	O
of	O
working	O
plugins	O
released	O
with	O
Tagsistant	B-Application
0.6	O
is	O
limited	O
to	O
:	O
</s>
<s>
Each	O
Tagsistant	B-Application
file	B-Application
system	I-Application
has	O
a	O
corresponding	O
repository	O
containing	O
an	O
archive/	O
directory	B-Application
where	O
the	O
objects	O
are	O
actually	O
saved	O
and	O
a	O
tags.sql	O
file	O
holding	O
tagging	O
information	O
as	O
an	O
SQLite	B-Language
database	O
.	O
</s>
<s>
If	O
the	O
MySQL	B-Application
database	O
engine	O
was	O
specified	O
with	O
the	O
--db	O
argument	O
,	O
the	O
tags.sql	O
file	O
will	O
be	O
empty	O
.	O
</s>
<s>
Another	O
file	O
named	O
repository.ini	O
is	O
a	O
GLib	B-Language
ini	O
store	O
with	O
the	O
repository	O
configuration	O
.	O
</s>
<s>
Tagsistant	B-Application
0.6	O
is	O
compatible	O
with	O
the	O
MySQL	B-Application
and	O
Sqlite	B-Language
dialects	O
of	O
SQL	O
for	O
tag	B-General_Concept
reasoning	O
and	O
tagging	O
resolution	O
.	O
</s>
<s>
The	O
archive/	O
directory	B-Application
has	O
been	O
introduced	O
to	O
provide	O
a	O
quick	O
way	O
to	O
access	O
objects	O
without	O
using	O
tags	B-General_Concept
.	O
</s>
<s>
The	O
stats/	O
directory	B-Application
features	O
some	O
read-only	O
files	B-Operating_System
containing	O
usage	O
statistics	O
.	O
</s>
<s>
It	O
has	O
been	O
highlighted	O
that	O
relying	O
on	O
an	O
external	O
database	O
to	O
store	O
tags	B-General_Concept
and	O
tagging	O
information	O
could	O
cause	O
the	O
complete	O
loss	O
of	O
metadata	O
if	O
the	O
database	O
gets	O
corrupted	O
.	O
</s>
<s>
It	O
has	O
been	O
highlighted	O
that	O
using	O
a	O
flat	O
namespace	O
tends	O
to	O
overcrowd	O
the	O
tags/	O
directory	B-Application
.	O
</s>
<s>
This	O
could	O
be	O
mitigated	O
introducing	O
triple	O
tags	B-General_Concept
.	O
</s>
