<s>
in	O
some	O
graph	B-Application
(	O
possibly	O
implicit	B-Data_Structure
)	O
of	O
objects	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
path	B-Operating_System
expression	I-Operating_System
p.Manager.Home.City	O
might	O
refer	O
the	O
city	O
of	O
residence	O
of	O
someone	O
's	O
manager	O
.	O
</s>
<s>
Path	B-Operating_System
expressions	I-Operating_System
have	O
been	O
extended	O
to	O
support	O
regular	O
expression-like	O
flexibility	O
.	O
</s>
<s>
XPath	B-Language
is	O
an	O
example	O
of	O
a	O
path	B-Operating_System
expression	I-Operating_System
language	O
.	O
</s>
<s>
In	O
concurrency	B-Operating_System
control	I-Operating_System
,	O
path	B-Operating_System
expressions	I-Operating_System
are	O
a	O
mechanism	O
for	O
expressing	O
permitted	O
sequences	O
of	O
execution	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
path	B-Operating_System
expression	I-Operating_System
like	O
"	O
{read},	O
write	O
"	O
might	O
specify	O
that	O
either	O
multiple	O
simultaneous	O
executions	O
of	O
read	O
or	O
a	O
single	O
execution	O
of	O
write	O
but	O
not	O
both	O
are	O
allowed	O
at	O
any	O
point	O
in	O
time	O
.	O
</s>
<s>
It	O
is	O
important	O
to	O
know	O
that	O
the	O
path	B-Operating_System
expressions	I-Operating_System
are	O
a	O
mechanism	O
for	O
the	O
synchronization	O
of	O
processes	O
at	O
the	O
monitor	O
level	O
in	O
the	O
software	O
.	O
</s>
<s>
In	O
addition	O
,	O
path	B-Operating_System
expressions	I-Operating_System
are	O
useful	O
for	O
process	O
synchronization	O
for	O
two	O
reasons	O
:	O
first	O
,	O
the	O
close	O
relationship	O
between	O
stream	O
expressions	O
and	O
regular	B-Language
expressions	I-Language
that	O
simplify	O
the	O
task	O
of	O
writing	O
and	O
reasoning	O
about	O
programs	O
that	O
use	O
this	O
synchronization	O
mechanism	O
.	O
</s>
<s>
Second	O
,	O
synchronization	O
in	O
many	O
concurrent	O
programs	O
in	O
a	O
finite	O
state	O
,	O
and	O
therefore	O
can	O
be	O
adequately	O
described	O
by	O
regular	B-Language
expressions	I-Language
.	O
</s>
<s>
For	O
precisely	O
the	O
same	O
reasons	O
,	O
path	B-Operating_System
expressions	I-Operating_System
are	O
useful	O
for	O
controlling	O
the	O
behavior	O
of	O
complicated	O
asynchronous	O
circuits	O
.	O
</s>
<s>
Path	B-Operating_System
expressions	I-Operating_System
provide	O
a	O
high	O
level	O
of	O
descriptive	O
synchronization	O
that	O
aids	O
in	O
the	O
prevention	O
and	O
detection	O
of	O
design	O
errors	O
in	O
complex	O
systems	O
and	O
overcomes	O
some	O
of	O
the	O
dangers	O
,	O
such	O
as	O
certain	O
forms	O
of	O
coding	O
errors	O
.	O
</s>
