<s>
A	O
collaborative	B-Application
real-time	I-Application
editor	I-Application
is	O
a	O
type	O
of	O
collaborative	B-Application
software	I-Application
or	O
web	B-Application
application	I-Application
which	O
enables	O
real-time	B-Application
collaborative	I-Application
editing	I-Application
,	O
simultaneous	B-Application
editing	I-Application
,	O
or	O
live	O
editing	O
of	O
the	O
same	O
digital	B-Protocol
document	I-Protocol
,	O
computer	B-Operating_System
file	I-Operating_System
or	O
cloud-stored	O
data	B-General_Concept
–	O
such	O
as	O
an	O
online	O
spreadsheet	B-Application
,	O
word	B-General_Concept
processing	I-General_Concept
document	O
,	O
database	O
or	O
presentation	B-Application
–	O
at	O
the	O
same	O
time	O
by	O
different	O
users	O
on	O
different	O
computers	O
or	O
mobile	B-Device
devices	I-Device
,	O
with	O
automatic	O
and	O
nearly	O
instantaneous	O
merging	O
of	O
their	O
edits	O
.	O
</s>
<s>
This	O
is	O
designed	O
to	O
avoid	O
or	O
minimize	O
edit	B-Operating_System
conflicts	I-Operating_System
.	O
</s>
<s>
non-real-time	O
,	O
delayed	O
or	O
offline	O
)	O
,	O
each	O
user	O
must	O
typically	O
manually	O
submit	O
(	O
publish	O
,	O
push	O
or	O
commit	O
)	O
,	O
update	O
(	O
refresh	O
,	O
pull	O
,	O
download	O
or	O
sync	O
)	O
and	O
(	O
if	O
any	O
edit	B-Operating_System
conflicts	I-Operating_System
occur	O
)	O
merge	B-General_Concept
their	O
edits	O
.	O
</s>
<s>
Due	O
to	O
the	O
delayed	O
nature	O
of	O
asynchronous	O
collaborative	O
editing	O
,	O
multiple	O
users	O
can	O
end	O
up	O
editing	O
the	O
same	O
line	O
,	O
word	B-Application
,	O
element	O
,	O
data	B-General_Concept
,	O
row	B-Application
or	O
field	B-Application
resulting	O
in	O
edit	B-Operating_System
conflicts	I-Operating_System
which	O
require	O
manual	O
edit	B-General_Concept
merging	I-General_Concept
or	O
overwriting	O
,	O
requiring	O
the	O
user	O
to	O
choose	O
which	O
edits	O
to	O
use	O
or	O
(	O
depending	O
on	O
the	O
system	O
and	O
setup	O
)	O
automatically	O
overwriting	O
their	O
edits	O
or	O
other	O
people	O
's	O
edits	O
,	O
with	O
or	O
without	O
a	O
warning	O
.	O
</s>
<s>
The	O
first	O
instance	O
of	O
a	O
collaborative	B-Application
real-time	I-Application
editor	I-Application
was	O
demonstrated	O
by	O
Douglas	O
Engelbart	O
in	O
1968	O
,	O
in	O
The	O
Mother	O
of	O
All	O
Demos	O
.	O
</s>
<s>
A	O
piece	O
of	O
software	O
called	O
Instant	O
Update	O
was	O
released	O
for	O
the	O
classic	B-Application
Mac	I-Application
OS	I-Application
in	O
1991	O
from	O
ON	O
Technology	O
.	O
</s>
<s>
It	O
allowed	O
real-time	O
editing	O
of	O
a	O
single	O
document	O
by	O
multiple	O
users	O
over	O
a	O
LAN	B-General_Concept
and	O
relied	O
on	O
a	O
workgroup	B-Device
server	B-Application
.	O
</s>
<s>
Interest	O
in	O
real-time	B-Application
collaborative	I-Application
editing	I-Application
over	O
the	O
internet	O
led	O
to	O
the	O
development	O
of	O
MoonEdit	B-Application
and	O
SubEthaEdit	B-Operating_System
in	O
the	O
2003-2005	O
time	O
frame	O
,	O
followed	O
soon	O
after	O
by	O
Gobby	B-Protocol
.	O
</s>
<s>
With	O
the	O
introduction	O
of	O
Ajax	B-General_Concept
technology	O
and	O
the	O
"	O
content	O
editable	O
"	O
function	O
in	O
browsers	O
,	O
web-based	B-Application
collaborative	O
editing	O
in	O
real-time	O
developed	O
as	O
part	O
of	O
the	O
Web	O
2.0	O
phenomenon	O
around	O
2005	O
.	O
</s>
<s>
In	O
particular	O
,	O
a	O
product	O
called	O
Writely	O
saw	O
explosive	O
user	O
growth	O
and	O
was	O
bought	O
by	O
Google	O
in	O
March	O
2006	O
(	O
what	O
became	O
known	O
as	O
Google	B-Application
Docs	I-Application
and	O
later	O
renamed	O
to	O
Google	B-Application
Drive	I-Application
)	O
.	O
</s>
<s>
It	O
provided	O
simultaneous	B-Application
edits	I-Application
on	O
the	O
entirety	O
of	O
a	O
document	O
,	O
though	O
changes	O
from	O
other	O
users	O
were	O
only	O
reflected	O
after	O
the	O
client	O
program	O
polling	O
the	O
server	B-Application
(	O
every	O
half-minute	O
or	O
so	O
)	O
.	O
</s>
<s>
Another	O
early	O
web-based	B-Application
solution	O
was	O
JotSpotLive	O
,	O
in	O
which	O
line-by-line	O
simultaneous	B-Application
editing	I-Application
was	O
available	O
in	O
near-realtime	O
.	O
</s>
<s>
However	O
,	O
after	O
Google	O
's	O
purchase	O
of	O
parent	O
company	O
JotSpot	B-Application
in	O
November	O
2006	O
,	O
the	O
site	O
was	O
closed	O
.	O
</s>
<s>
Google	B-Application
Sites	I-Application
was	O
launched	O
in	O
February	O
2007	O
as	O
a	O
refactoring	O
of	O
JotSpot	B-Application
,	O
but	O
it	O
lacks	O
the	O
multi-user	O
real-time	O
abilities	O
of	O
JotLive	O
.	O
</s>
<s>
The	O
Synchroedit	O
(	O
rich	O
text	O
)	O
and	O
MobWrite	O
(	O
plain	O
text	O
)	O
projects	O
are	O
two	O
,	O
more	O
recent	O
,	O
open	O
source	O
attempts	O
to	O
fill	O
the	O
gap	O
in	O
real-time	O
browser-based	B-Application
collaborative	O
editing	O
,	O
though	O
still	O
unable	O
to	O
achieve	O
true	O
real-time	O
performance	O
,	O
especially	O
on	O
a	O
large	O
scale	O
architecture	O
.	O
</s>
<s>
In	O
2009	O
,	O
Google	O
started	O
beta	O
testing	O
Google	B-Application
Wave	I-Application
,	O
a	O
real-time	O
collaboration	O
environment	O
which	O
Google	O
hoped	O
would	O
eventually	O
displace	O
email	O
and	O
instant	O
messaging	O
.	O
</s>
<s>
EtherPad	B-Language
was	O
acquired	O
by	O
Google	O
,	O
which	O
allocated	O
the	O
EtherPad	B-Language
team	O
to	O
work	O
within	O
the	O
Wave	O
project	O
.	O
</s>
<s>
After	O
Google	O
released	O
the	O
abandoned	O
EtherPad	B-Language
source	O
code	O
as	O
open	O
source	O
in	O
December	O
2009	O
,	O
the	O
community	O
took	O
over	O
its	O
development	O
and	O
produced	O
a	O
complete	O
rewrite	O
named	O
Etherpad	B-Language
lite	O
,	O
which	O
is	O
written	O
entirely	O
in	O
JavaScript	B-Language
and	O
built	O
on	O
top	O
of	O
Node.js	B-Language
.	O
</s>
<s>
Another	O
notable	O
tools	O
based	O
on	O
operational	B-Operating_System
transformation	I-Operating_System
technology	O
is	O
CKEditor	B-Application
.	O
</s>
<s>
2020	O
has	O
seen	O
a	O
surge	O
of	O
interest	O
in	O
the	O
concept	O
,	O
as	O
Microsoft	O
also	O
recently	O
released	O
its	O
Fluid	O
framework	O
,	O
which	O
relies	O
on	O
a	O
novel	O
Total	O
Order	O
Broadcast	O
technology	O
,	O
as	O
opposed	O
to	O
OT	O
or	O
CRDT	B-Operating_System
.	O
</s>
<s>
In	O
June	O
2016	O
,	O
Collabora	O
Productivity	O
released	O
V1.0	O
of	O
Collabora	B-General_Concept
Online	I-General_Concept
,	O
an	O
open	O
source	O
online	O
office	O
suite	O
using	O
LibreOffice	B-Application
Technology	O
,	O
it	O
can	O
be	O
integrated	O
into	O
any	O
website	O
with	O
a	O
few	O
lines	O
of	O
code	O
.	O
</s>
<s>
A	O
software	B-Application
development	I-Application
kit	I-Application
exists	O
with	O
sample	O
integration	O
code	O
in	O
several	O
languages	O
Node.js	B-Language
,	O
PHP	B-Application
,	O
Python	B-Language
,	O
ReactJS	O
and	O
.NET	B-Application
,	O
these	O
have	O
API	B-General_Concept
specifications	O
allowing	O
interoperable	O
integrations	O
with	O
customizable	O
user	O
interfaces	O
.	O
</s>
<s>
With	O
Collabora	B-General_Concept
Online	I-General_Concept
documents	O
remain	O
on	O
the	O
server	B-Application
,	O
each	O
user	O
shares	O
the	O
same	O
document	O
concurrently	O
allowing	O
just	O
one	O
document	O
to	O
be	O
edited	O
in	O
real-time	O
and	O
interactively	O
with	O
no	O
extra	O
lag	O
or	O
latency	O
to	O
see	O
other	O
users’	O
typing	O
.	O
</s>
<s>
It	O
enables	O
collaborative	B-Application
real-time	I-Application
editing	I-Application
of	O
word	B-General_Concept
processing	I-General_Concept
documents	O
,	O
spreadsheets	B-Application
,	O
presentations	O
,	O
drawing	O
and	O
vector	O
graphics	O
.	O
</s>
<s>
Recently	O
,	O
real-time	B-Application
collaborative	I-Application
editing	I-Application
has	O
returned	O
to	O
stand-alone	O
text	O
editing	O
applications	O
with	O
extensions	O
for	O
Atom	B-Application
and	O
Visual	B-Language
Studio	I-Language
Code	I-Language
released	O
in	O
2020	O
.	O
</s>
<s>
Real-time	B-Application
collaborative	I-Application
editing	I-Application
can	O
occur	O
online	O
in	O
web	B-Application
applications	I-Application
such	O
as	O
Microsoft	B-Application
Office	I-Application
on	I-Application
the	I-Application
web	I-Application
(	O
formerly	O
Office	O
Online	O
)	O
–	O
which	O
supports	O
online	O
(	O
web-based	B-Application
)	O
simultaneous	B-Application
editing	I-Application
(	O
which	O
Microsoft	O
refers	O
to	O
as	O
"	O
Co-Authoring	O
"	O
)	O
of	O
Word	B-Application
documents	O
,	O
Excel	B-Application
spreadsheets	B-Application
,	O
PowerPoint	B-Application
and	O
other	O
Microsoft	B-Application
Office	I-Application
documents	O
stored	O
on	O
Office.com,	O
OneDrive	B-Application
or	O
SharePoint	B-Protocol
cloud	O
storage	O
–	O
or	O
Google	B-Application
Docs	I-Application
and	O
other	O
Google	B-Application
Workspace	I-Application
productivity	O
(	O
office	O
suite	O
)	O
apps	O
–	O
for	O
online	O
collaborative	O
editing	O
of	O
word	B-General_Concept
processing	I-General_Concept
and	O
other	O
documents	O
stored	O
in	O
Google	B-Application
Drive	I-Application
.	O
</s>
<s>
Real-time	B-Application
collaborative	I-Application
editing	I-Application
can	O
also	O
occur	O
in	O
hybrid	O
manner	O
,	O
such	O
as	O
with	O
Power	O
Sheet	O
BI	O
for	O
Excel	B-Application
,	O
in	O
offline	O
,	O
web-based	B-Application
,	O
and	O
online	O
collaborative	O
editing	O
in	O
desktop	O
software	O
as	O
well	O
as	O
web-based	B-Application
and	O
mobile	O
apps	O
,	O
which	O
can	O
be	O
synchronized	O
automatically	O
with	O
instant	O
access	O
to	O
version	O
history	O
.	O
</s>
<s>
2020	O
has	O
seen	O
a	O
resurgence	O
of	O
interest	O
in	O
embedding	O
these	O
applications	O
into	O
secure	O
web	B-Application
applications	I-Application
,	O
particularly	O
for	O
business	O
use-cases	O
,	O
with	O
Microsoft	O
and	O
Vaadin	B-Language
taking	O
the	O
lead	O
with	O
specialized	O
real-time	O
collaboration	O
backends	O
that	O
handle	O
the	O
complexities	O
of	O
real-time	O
synchronous	O
data	B-General_Concept
sharing	O
,	O
which	O
developers	O
can	O
utilize	O
through	O
APIs	B-General_Concept
.	O
</s>
<s>
Mozilla	O
released	O
in	O
2013	O
the	O
javascript	B-Language
library	O
TogetherJS	O
,	O
which	O
adds	O
real-time	B-Application
collaborative	I-Application
editing	I-Application
to	O
any	O
web	B-Application
application	I-Application
via	O
a	O
messaging	O
system	O
and	O
optionally	O
an	O
operational	B-Operating_System
transform	I-Operating_System
algorithm	O
for	O
forms	O
synchronization	O
.	O
</s>
<s>
Vaadin	B-Language
Ltd.	O
,	O
the	O
vendor	O
of	O
the	O
Vaadin	B-Language
platform	O
,	O
released	O
V1.0	O
of	O
their	O
Collaboration	O
Engine	O
In	O
October	O
2020	O
,	O
with	O
the	O
premise	O
of	O
allowing	O
developers	O
to	O
rapidly	O
build	O
real-time	O
collaboration	O
and	O
editing	O
features	O
in	O
to	O
any	O
web	B-Application
application	I-Application
with	O
Java	O
backends	O
using	O
a	O
few	O
lines	O
of	O
codes	O
(	O
for	O
specific	O
use-cases	O
through	O
their	O
,	O
still	O
limited	O
,	O
high-level	O
APIs	B-General_Concept
)	O
.	O
</s>
<s>
This	O
feature	O
currently	O
supports	O
Java	O
,	O
although	O
the	O
vendor	O
notes	O
that	O
a	O
TypeScript-based	O
API	B-General_Concept
is	O
also	O
incoming	O
,	O
in	O
line	O
with	O
the	O
Vaadin	B-Language
platform	O
's	O
recent	O
ongoing	O
expansion	O
into	O
also	O
enabling	O
TypeScript-based	O
UI	O
building	O
in	O
the	O
future	O
through	O
its	O
upcoming	O
Fusion	O
framework	O
.	O
</s>
<s>
The	O
complexity	O
of	O
real-time	B-Application
collaborative	I-Application
editing	I-Application
solutions	O
stems	O
from	O
communication	O
latency	O
.	O
</s>
<s>
In	O
theory	O
,	O
if	O
communication	O
were	O
instantaneous	O
,	O
then	O
creating	O
a	O
real-time	B-Application
collaborative	I-Application
editor	I-Application
would	O
be	O
no	O
more	O
difficult	O
than	O
creating	O
a	O
single-user	O
editor	O
,	O
because	O
a	O
document	O
could	O
be	O
edited	O
using	O
an	O
algorithm	O
similar	O
to	O
the	O
following	O
:	O
</s>
<s>
Suppose	O
Bob	O
and	O
Alice	O
start	O
with	O
a	O
document	O
containing	O
the	O
word	B-Application
Mary	O
.	O
</s>
<s>
Bob	O
deletes	O
'	O
M	O
 '	O
,	O
then	O
inserts	O
'	O
H	O
 '	O
,	O
to	O
change	O
the	O
word	B-Application
into	O
Hary	O
.	O
</s>
<s>
Thus	O
,	O
the	O
challenge	O
of	O
real-time	B-Application
collaborative	I-Application
editing	I-Application
is	O
to	O
figure	O
out	O
exactly	O
how	O
to	O
apply	O
edits	O
from	O
remote	O
users	O
,	O
which	O
were	O
originally	O
created	O
in	O
versions	O
of	O
the	O
document	O
that	O
never	O
existed	O
locally	O
,	O
and	O
which	O
may	O
conflict	O
with	O
the	O
user	O
's	O
own	O
local	O
edits	O
.	O
</s>
<s>
The	O
most	O
sophisticated	O
solutions	O
solve	O
this	O
problem	O
in	O
a	O
way	O
that	O
does	O
not	O
require	O
a	O
server	B-Application
,	O
does	O
not	O
use	O
locking	O
(	O
all	O
users	O
can	O
freely	O
edit	O
all	O
parts	O
of	O
a	O
document	O
at	O
the	O
same	O
time	O
)	O
,	O
and	O
supports	O
any	O
number	O
of	O
users	O
(	O
limited	O
only	O
by	O
the	O
resources	O
of	O
the	O
computers	O
)	O
.	O
</s>
<s>
UNA	O
and	O
SubEthaEdit	B-Operating_System
are	O
examples	O
of	O
two	O
programs	O
that	O
take	O
this	O
approach	O
.	O
</s>
<s>
While	O
these	O
sophisticated	O
approaches	O
enable	O
the	O
best	O
user	B-Application
experience	I-Application
,	O
a	O
basic	O
collaborative	B-Application
editor	I-Application
can	O
also	O
be	O
created	O
in	O
a	O
client	B-Operating_System
–	I-Operating_System
server	I-Operating_System
model	I-Operating_System
.	O
</s>
<s>
In	O
a	O
client	B-Operating_System
–	I-Operating_System
server	I-Operating_System
scenario	O
,	O
one	O
of	O
the	O
editor	O
instances	O
is	O
assigned	O
the	O
role	O
of	O
collaboration	O
server	B-Application
when	O
the	O
document	O
is	O
opened	O
.	O
</s>
<s>
This	O
server	B-Application
ensures	O
that	O
other	O
editors	O
are	O
kept	O
in	O
sync	O
by	O
determining	O
network	O
latency	O
and	O
acting	O
as	O
a	O
time	O
synchronization	O
server	B-Application
.	O
</s>
<s>
The	O
server	B-Application
receives	O
timestamped	O
notifications	O
of	O
changes	O
made	O
to	O
the	O
document	O
by	O
other	O
users	O
.	O
</s>
<s>
In	O
some	O
models	O
,	O
the	O
changes	O
are	O
not	O
reflected	O
on	O
a	O
client	O
until	O
an	O
official	O
response	O
is	O
returned	O
from	O
the	O
server	B-Application
,	O
even	O
if	O
those	O
changes	O
were	O
made	O
locally	O
.	O
</s>
