<s>
Kinetic	B-Language
Rule	I-Language
Language	I-Language
(	O
KRL	O
)	O
is	O
a	O
rule-based	O
programming	O
language	O
for	O
creating	O
applications	O
on	O
the	O
Live	O
Web	O
.	O
</s>
<s>
KRL	O
has	O
been	O
promoted	O
as	O
language	O
for	O
building	O
personal	B-General_Concept
clouds	I-General_Concept
.	O
</s>
<s>
KRL	O
is	O
part	O
of	O
an	O
open-source	B-License
project	O
called	O
KRE	O
,	O
for	O
Kinetic	O
Rules	O
Engine	O
,	O
developed	O
by	O
Kynetx	B-Language
,	O
Inc	O
.	O
</s>
<s>
KRL	O
was	O
designed	O
by	O
Phil	O
Windley	O
at	O
Kynetx	B-Language
,	O
beginning	O
in	O
2007	O
.	O
</s>
<s>
Development	O
of	O
the	O
language	O
has	O
since	O
expanded	O
to	O
include	O
libraries	O
and	O
modules	O
for	O
a	O
variety	O
of	O
web	O
services	O
,	O
including	O
Twitter	B-Application
,	O
Facebook	B-Application
,	O
and	O
Twilio	B-General_Concept
.	O
</s>
<s>
In	O
event-driven	B-Application
programming	I-Application
,	O
events	O
,	O
a	O
notification	O
that	O
something	O
happened	O
,	O
control	O
the	O
flow	O
of	O
execution	O
.	O
</s>
<s>
The	O
entity	O
orientation	O
of	O
KRL	O
is	O
supported	O
by	O
the	O
underlying	O
KRE	O
(	O
Kynetx	B-Language
Rules	O
Engine	O
)	O
and	O
so	O
is	O
usable	O
by	O
any	O
program	O
running	O
in	O
the	O
engine	O
—	O
even	O
one	O
not	O
written	O
in	O
KRL	O
.	O
</s>
<s>
Both	O
are	O
closed	B-Language
over	O
the	O
ruleset	O
they	O
are	O
in	O
,	O
meaning	O
that	O
they	O
are	O
only	O
visible	O
to	O
code	O
executing	O
within	O
the	O
ruleset	O
.	O
</s>
<s>
Application	O
variables	O
are	O
roughly	O
analogous	O
to	O
class	B-Application
variables	I-Application
.	O
</s>
<s>
Entity	O
variables	O
are	O
like	O
instance	B-Application
variables	I-Application
.	O
</s>
<s>
Because	O
a	O
ruleset	O
represents	O
a	O
closure	B-Language
over	O
its	O
entity	O
variables	O
,	O
every	O
ruleset	O
potentially	O
represents	O
a	O
persistent	O
data	O
object	O
.	O
</s>
<s>
KRL	O
is	O
called	O
an	O
event	B-General_Concept
condition	I-General_Concept
action	I-General_Concept
or	O
ECA	O
rule	O
language	O
because	O
of	O
the	O
roles	O
that	O
those	O
three	O
fundamental	O
parts	O
of	O
a	O
rule	O
play	O
:	O
</s>
<s>
Because	O
the	O
Evented	O
API	O
is	O
a	O
specialization	O
of	O
the	O
webhook	B-Protocol
concept	O
,	O
any	O
system	O
that	O
supports	O
webhooks	B-Protocol
can	O
raise	O
events	O
for	O
KRL	O
.	O
</s>
<s>
An	O
endpoint	O
that	O
generates	O
an	O
event	O
may	O
be	O
observing	O
some	O
activity	O
directly	O
and	O
reporting	O
salient	O
state	O
changes	O
or	O
it	O
might	O
just	O
be	O
reporting	O
or	O
transforming	O
event	O
data	O
from	O
another	O
source	O
(	O
e.g.	O
,	O
a	O
webhook	B-Protocol
)	O
.	O
</s>
<s>
Just	O
as	O
functional	B-Language
,	O
object-oriented	B-Language
,	O
and	O
imperative	B-Application
languages	I-Application
are	O
all	O
different	O
,	O
rule	O
languages	O
also	O
require	O
a	O
different	O
way	O
of	O
thinking	O
.	O
</s>
<s>
Interrogatory-style	O
systems	O
use	O
a	O
request-response	O
mode	O
of	O
interaction	O
:	O
“	O
Will	O
you	O
do	O
this	O
?	O
”	O
Imperative-style	O
systems	O
use	O
an	O
RPC	B-Operating_System
mode	O
of	O
interaction	O
:	O
“	O
Do	O
this	O
!	O
”	O
In	O
contrast	O
,	O
event	O
interactions	O
are	O
declarative	O
,	O
stating	O
only	O
that	O
a	O
specific	O
state	O
change	O
happened	O
:	O
“	O
This	O
happened	O
”	O
.	O
</s>
