<s>
Merb	B-Application
is	O
a	O
discontinued	O
model	O
–	O
view	O
–	O
controller	O
web	B-Application
framework	I-Application
in	O
Ruby	B-Language
,	O
notable	O
as	O
a	O
precursor	O
to	O
Rails	B-Application
3	O
.	O
</s>
<s>
It	O
brought	O
increased	O
focus	O
on	O
speed	O
and	O
modularity	B-Architecture
to	O
Rails	B-Application
3	O
.	O
</s>
<s>
The	O
name	O
Merb	B-Application
is	O
a	O
contraction	O
of	O
"	O
Mongrel	B-Application
"	O
and	O
"	O
Erb	O
"	O
.	O
</s>
<s>
Merb	B-Application
began	O
as	O
a	O
"	O
clean-room	O
"	O
implementation	O
of	O
the	O
Rails	B-Application
controller	O
stack	O
but	O
grew	O
to	O
incorporate	O
several	O
ideas	O
that	O
deviated	O
from	O
Rails	B-Application
's	O
spirit	O
and	O
methodology	O
at	O
the	O
time	O
,	O
most	O
notably	O
component	B-Architecture
modularity	I-Architecture
,	O
extensible	O
API	O
design	O
,	O
and	O
vertical	O
scalability	O
.	O
</s>
<s>
Most	O
of	O
these	O
capabilities	O
were	O
added	O
to	O
Rails	B-Application
during	O
the	O
Rails	B-Application
3/Merb	O
merger	O
.	O
</s>
<s>
Merb	B-Application
was	O
first	O
released	O
at	O
the	O
2008	O
RubyConf	B-Language
and	O
development	O
has	O
since	O
stopped	O
;	O
Rails	B-Application
3	O
,	O
therefore	O
,	O
serves	O
as	O
both	O
the	O
successor	O
to	O
Rails	B-Application
2	O
and	O
the	O
successor	O
to	O
Merb	B-Application
.	O
</s>
<s>
Merb	B-Application
's	O
design	O
attempted	O
to	O
address	O
several	O
criticisms	O
of	O
Rails	B-Application
2	O
:	O
</s>
<s>
Merb	B-Application
itself	O
encompassed	O
only	O
the	O
controller	O
layer	O
in	O
MVC	O
architecture	O
,	O
and	O
used	O
a	O
suite	O
of	O
complementary	O
,	O
optional	O
plugins	O
together	O
to	O
assemble	O
applications	O
.	O
</s>
<s>
Merb	B-Application
's	O
default	O
application	O
stack	O
incorporated	O
Datamapper	B-Application
for	O
models	O
,	O
ERB	O
for	O
views	O
,	O
and	O
Rack	B-Application
and	O
Mongrel	B-Application
as	O
the	O
web	O
server	O
layer	O
.	O
</s>
<s>
Before	O
the	O
Merb	B-Application
/	O
Rails	B-Application
3	O
merge	O
,	O
Rails	B-Application
lacked	O
a	O
well-defined	O
,	O
documented	O
,	O
public	O
API	O
for	O
extensions	O
and	O
plug-ins	O
,	O
leading	O
to	O
issues	O
when	O
Rails	B-Application
changes	O
broke	O
monkey-patches	B-Application
performed	O
by	O
plug-ins	O
.	O
</s>
<s>
With	O
the	O
Rails	B-Application
3	O
/	O
Merb	B-Application
merge	O
,	O
Rails	B-Application
gained	O
a	O
defined	O
public	O
API	O
with	O
a	O
test	O
suite	O
,	O
giving	O
users	O
and	O
plugin	O
developers	O
a	O
clearer	O
,	O
more	O
stable	O
API	O
to	O
build	O
against	O
,	O
reducing	O
plugin	O
breakage	O
from	O
release	O
to	O
release	O
.	O
</s>
<s>
Some	O
early	O
versions	O
of	O
Rails	B-Application
received	O
bad	O
publicity	O
for	O
lack	O
of	O
performance	O
,	O
frequently	O
due	O
to	O
developer	O
confusion	O
about	O
ActiveRecord	O
queries	O
.	O
</s>
<s>
David	O
Heinemeier	O
Hansson	O
,	O
the	O
creator	O
of	O
Rails	B-Application
,	O
stated	O
that	O
Merb	B-Application
re-wrote	O
many	O
core	O
Rails	B-Application
pieces	O
to	O
be	O
faster	O
,	O
and	O
incorporated	O
those	O
changes	O
from	O
Merb	B-Application
in	O
the	O
Rails	B-Application
3	O
merge	O
,	O
promising	O
users	O
that	O
"	O
Rails	B-Application
3	O
will	O
get	O
all	O
the	O
performance	O
attention	O
that	O
the	O
Merb	B-Application
guys	O
are	O
known	O
for	O
"	O
.	O
</s>
