<s>
Petname	B-Operating_System
systems	O
are	O
naming	O
systems	O
that	O
claim	O
to	O
possess	O
all	O
three	O
naming	O
properties	O
of	O
Zooko	O
's	O
triangle	O
-	O
global	O
,	O
secure	O
,	O
and	O
memorable	O
.	O
</s>
<s>
Unlike	O
traditional	O
identity	O
systems	O
,	O
which	O
focus	O
on	O
the	O
service	O
provider	O
,	O
Petname	B-Operating_System
systems	O
are	O
decentralized	O
and	O
designed	O
to	O
facilitate	O
the	O
needs	O
of	O
the	O
enduser	O
as	O
they	O
interact	O
with	O
multiple	O
services	O
.	O
</s>
<s>
Though	O
the	O
Petname	B-Operating_System
model	O
was	O
formally	O
described	O
in	O
2005	O
by	O
Mark	O
Stiegler	O
,	O
the	O
potential	O
of	O
the	O
system	O
was	O
discovered	O
by	O
several	O
people	O
successively	O
.	O
</s>
<s>
Petname	B-Operating_System
Tool	I-Operating_System
(	O
discontinued	O
browser	O
extension	B-Operating_System
)	O
–	O
There	O
was	O
a	O
browser	O
extension	B-Operating_System
available	O
for	O
Firefox	B-Application
called	O
Petname	B-Operating_System
Tool	I-Operating_System
that	O
allowed	O
pet	O
names	O
to	O
be	O
assigned	O
to	O
secure	O
websites	O
.	O
</s>
<s>
Use	O
of	O
this	O
extension	B-Operating_System
could	O
help	O
prevent	O
phishing	O
attacks	O
.	O
</s>
<s>
The	O
PetName	B-Operating_System
Markup	I-Operating_System
Language	I-Operating_System
(	O
PNML	O
)	O
is	O
a	O
proposal	O
for	O
embedding	O
Petname	B-Operating_System
information	O
into	O
other	O
systems	O
using	O
a	O
custom	O
markup	O
language	O
.	O
</s>
