<s>
A	O
tag	B-Application
cloud	I-Application
(	O
also	O
known	O
as	O
a	O
word	B-Application
cloud	I-Application
,	O
wordle	O
or	O
weighted	B-Application
list	I-Application
in	O
visual	O
design	O
)	O
is	O
a	O
visual	O
representation	O
of	O
text	O
data	O
,	O
which	O
is	O
often	O
used	O
to	O
depict	O
keyword	B-General_Concept
metadata	I-General_Concept
on	O
websites	O
,	O
or	O
to	O
visualize	O
free	O
form	O
text	O
.	O
</s>
<s>
Tags	B-General_Concept
are	O
usually	O
single	O
words	O
,	O
and	O
the	O
importance	O
of	O
each	O
tag	B-General_Concept
is	O
shown	O
with	O
font	O
size	O
or	O
color	O
.	O
</s>
<s>
When	O
used	O
as	O
website	O
navigation	O
aids	O
,	O
the	O
terms	O
are	O
hyperlinked	O
to	O
items	O
associated	O
with	O
the	O
tag	B-General_Concept
.	O
</s>
<s>
In	O
the	O
language	O
of	O
visual	O
design	O
,	O
a	O
tag	B-Application
cloud	I-Application
(	O
or	O
word	B-Application
cloud	I-Application
)	O
is	O
one	O
kind	O
of	O
"	O
weighted	B-Application
list	I-Application
"	O
,	O
as	O
commonly	O
used	O
on	O
geographic	O
maps	O
to	O
represent	O
the	O
relative	O
size	O
of	O
cities	O
in	O
terms	O
of	O
relative	O
typeface	O
size	O
.	O
</s>
<s>
An	O
early	O
printed	O
example	O
of	O
a	O
weighted	B-Application
list	I-Application
of	O
English	O
keywords	O
was	O
the	O
"	O
subconscious	O
files	O
"	O
in	O
Douglas	O
Coupland	O
's	O
Microserfs	O
(	O
1995	O
)	O
.	O
</s>
<s>
The	O
specific	O
visual	O
form	O
and	O
common	O
use	O
of	O
the	O
term	O
"	O
tag	B-Application
cloud	I-Application
"	O
rose	O
to	O
prominence	O
in	O
the	O
first	O
decade	O
of	O
the	O
21st	O
century	O
as	O
a	O
widespread	O
feature	O
of	O
early	O
Web	O
2.0	O
websites	O
and	O
blogs	O
,	O
used	O
primarily	O
to	O
visualize	O
the	O
frequency	O
distribution	O
of	O
keyword	B-General_Concept
metadata	I-General_Concept
that	O
describe	O
website	O
content	O
,	O
and	O
as	O
a	O
navigation	O
aid	O
.	O
</s>
<s>
The	O
first	O
tag	B-Application
clouds	I-Application
on	O
a	O
high-profile	O
website	O
were	O
on	O
the	O
photo	O
sharing	O
site	O
Flickr	B-Algorithm
,	O
created	O
by	O
Flickr	B-Algorithm
co-founder	O
and	O
interaction	O
designer	O
Stewart	O
Butterfield	O
in	O
2004	O
.	O
</s>
<s>
Tag	B-Application
clouds	I-Application
were	O
also	O
popularized	O
around	O
the	O
same	O
time	O
by	O
Del.icio.us	B-Application
and	O
Technorati	B-Application
,	O
among	O
others	O
.	O
</s>
<s>
Oversaturation	O
of	O
the	O
tag	B-Application
cloud	I-Application
method	O
and	O
ambivalence	O
about	O
its	O
utility	O
as	O
a	O
web-navigation	O
tool	O
led	O
to	O
a	O
decline	O
of	O
usage	O
among	O
these	O
early	O
adopters	O
.	O
</s>
<s>
Flickr	B-Algorithm
gave	O
a	O
five-word	O
acceptance	O
speech	O
for	O
the	O
2006	O
"	O
Best	O
Practices	O
"	O
Webby	O
Award	O
,	O
which	O
simply	O
stated	O
"	O
sorry	O
about	O
the	O
tag	O
clouds.	O
"	O
</s>
<s>
A	O
second	O
generation	O
of	O
software	O
development	O
discovered	O
a	O
wider	O
diversity	O
of	O
uses	O
for	O
tag	B-Application
clouds	I-Application
as	O
a	O
basic	O
visualization	O
method	O
for	O
text	O
data	O
.	O
</s>
<s>
Several	O
extensions	O
of	O
tag	B-Application
clouds	I-Application
have	O
been	O
proposed	O
in	O
this	O
context	O
.	O
</s>
<s>
There	O
are	O
three	O
main	O
types	O
of	O
tag	B-Application
cloud	I-Application
applications	O
in	O
social	O
software	O
,	O
distinguished	O
by	O
their	O
meaning	O
rather	O
than	O
appearance	O
.	O
</s>
<s>
In	O
the	O
first	O
type	O
,	O
there	O
is	O
a	O
tag	B-General_Concept
for	O
the	O
frequency	O
of	O
each	O
item	O
,	O
whereas	O
in	O
the	O
second	O
type	O
,	O
there	O
are	O
global	O
tag	B-Application
clouds	I-Application
where	O
the	O
frequencies	O
are	O
aggregated	O
over	O
all	O
items	O
and	O
users	O
.	O
</s>
<s>
In	O
the	O
first	O
type	O
,	O
size	O
represents	O
the	O
number	O
of	O
times	O
that	O
tag	B-General_Concept
has	O
been	O
applied	O
to	O
a	O
single	O
item	O
.	O
</s>
<s>
In	O
the	O
second	O
,	O
more	O
commonly	O
used	O
type	O
,	O
size	O
represents	O
the	O
number	O
of	O
items	O
to	O
which	O
a	O
tag	B-General_Concept
has	O
been	O
applied	O
,	O
as	O
a	O
presentation	O
of	O
each	O
tag	B-General_Concept
's	O
popularity	O
.	O
</s>
<s>
In	O
the	O
third	O
type	O
,	O
tags	B-General_Concept
are	O
used	O
as	O
a	O
categorization	O
method	O
for	O
content	O
items	O
.	O
</s>
<s>
Tags	B-General_Concept
are	O
represented	O
in	O
a	O
cloud	O
where	O
larger	O
tags	B-General_Concept
represent	O
the	O
quantity	O
of	O
content	O
items	O
in	O
that	O
category	O
.	O
</s>
<s>
There	O
are	O
some	O
approaches	O
to	O
construct	O
tag	B-General_Concept
clusters	O
instead	O
of	O
tag	B-Application
clouds	I-Application
,	O
e.g.	O
,	O
by	O
applying	O
tag	B-General_Concept
co-occurrences	O
in	O
documents	O
.	O
</s>
<s>
More	O
generally	O
,	O
the	O
same	O
visual	O
technique	O
can	O
be	O
used	O
to	O
display	O
non-tag	O
data	O
,	O
as	O
in	O
a	O
word	B-Application
cloud	I-Application
or	O
a	O
data	B-Application
cloud	I-Application
.	O
</s>
<s>
The	O
term	O
keyword	B-Application
cloud	I-Application
is	O
sometimes	O
used	O
as	O
a	O
search	O
engine	O
marketing	O
(	O
SEM	O
)	O
term	O
that	O
refers	O
to	O
a	O
group	O
of	O
keywords	O
that	O
are	O
relevant	O
to	O
a	O
specific	O
website	O
.	O
</s>
<s>
In	O
recent	O
years	O
tag	B-Application
clouds	I-Application
have	O
gained	O
popularity	O
because	O
of	O
their	O
role	O
in	O
search	O
engine	O
optimization	O
of	O
Web	O
pages	O
as	O
well	O
as	O
supporting	O
the	O
user	O
in	O
navigating	O
the	O
content	O
in	O
an	O
information	O
system	O
efficiently	O
.	O
</s>
<s>
Tag	B-Application
clouds	I-Application
as	O
a	O
navigational	O
tool	O
make	O
the	O
resources	O
of	O
a	O
website	O
more	O
connected	O
,	O
when	O
crawled	O
by	O
a	O
search	O
engine	O
spider	O
,	O
which	O
may	O
improve	O
the	O
site	O
's	O
search	B-Algorithm
engine	I-Algorithm
rank	I-Algorithm
.	O
</s>
<s>
Tag	B-Application
clouds	I-Application
are	O
typically	O
represented	O
using	O
inline	O
HTML	B-Language
elements	O
.	O
</s>
<s>
The	O
tags	B-General_Concept
can	O
appear	O
in	O
alphabetical	O
order	O
,	O
in	O
a	O
random	O
order	O
,	O
they	O
can	O
be	O
sorted	O
by	O
weight	O
,	O
and	O
so	O
on	O
.	O
</s>
<s>
Most	O
popular	O
is	O
a	O
rectangular	O
tag	B-General_Concept
arrangement	O
with	O
alphabetical	O
sorting	O
in	O
a	O
sequential	O
line-by-line	O
layout	O
.	O
</s>
<s>
Some	O
prefer	O
to	O
cluster	O
the	O
tags	B-General_Concept
semantically	O
so	O
that	O
similar	O
tags	B-General_Concept
will	O
appear	O
near	O
each	O
other	O
or	O
use	O
embedding	B-General_Concept
techniques	O
such	O
as	O
tSNE	B-Algorithm
to	O
position	O
words	O
.	O
</s>
<s>
Edges	O
can	O
be	O
added	O
to	O
emphasize	O
the	O
co-occurrences	O
of	O
tags	B-General_Concept
and	O
visualize	O
interactions	O
.	O
</s>
<s>
Heuristics	B-Algorithm
can	O
be	O
used	O
to	O
reduce	O
the	O
size	O
of	O
the	O
tag	B-Application
cloud	I-Application
whether	O
or	O
not	O
the	O
purpose	O
is	O
to	O
cluster	O
the	O
tags	B-General_Concept
.	O
</s>
<s>
Tag	B-Application
cloud	I-Application
visual	O
taxonomy	O
is	O
determined	O
by	O
a	O
number	O
of	O
attributes	O
:	O
tag	B-General_Concept
ordering	O
rule	O
(	O
e.g.	O
</s>
<s>
rectangular	O
,	O
circle	O
,	O
given	O
map	O
borders	O
)	O
,	O
shape	O
of	O
tag	B-General_Concept
bounds	O
(	O
rectangle	O
,	O
or	O
character	O
body	O
)	O
,	O
tag	B-General_Concept
rotation	O
(	O
none	O
,	O
free	O
,	O
limited	O
)	O
,	O
vertical	O
tag	B-General_Concept
alignment	O
(	O
sticking	O
to	O
typographical	O
baselines	O
,	O
free	O
)	O
.	O
</s>
<s>
A	O
tag	B-Application
cloud	I-Application
on	O
the	O
web	O
must	O
address	O
problems	O
of	O
modeling	O
and	O
controlling	O
aesthetics	O
,	O
constructing	O
a	O
two-dimensional	O
layout	O
of	O
tags	B-General_Concept
,	O
and	O
all	O
these	O
must	O
be	O
done	O
in	O
short	O
time	O
on	O
volatile	O
browser	O
platform	O
.	O
</s>
<s>
Tags	B-General_Concept
clouds	O
to	O
be	O
used	O
on	O
the	O
web	O
must	O
be	O
in	O
HTML	B-Language
,	O
not	O
graphics	O
,	O
to	O
make	O
them	O
robot-readable	O
,	O
they	O
must	O
be	O
constructed	O
on	O
the	O
client	O
side	O
using	O
the	O
fonts	O
available	O
in	O
the	O
browser	O
,	O
and	O
they	O
must	O
fit	O
in	O
a	O
rectangular	O
box	O
.	O
</s>
<s>
A	O
data	B-Application
cloud	I-Application
or	O
cloud	O
data	O
is	O
a	O
data	O
display	O
which	O
uses	O
font	O
size	O
and/or	O
color	O
to	O
indicate	O
numerical	O
values	O
.	O
</s>
<s>
It	O
is	O
similar	O
to	O
a	O
tag	B-Application
cloud	I-Application
but	O
instead	O
of	O
word	O
count	O
,	O
displays	O
data	O
such	O
as	O
population	O
or	O
stock	O
market	O
prices	O
.	O
</s>
<s>
A	O
text	O
cloud	O
or	O
word	B-Application
cloud	I-Application
is	O
a	O
visualization	O
of	O
word	O
frequency	O
in	O
a	O
given	O
text	O
as	O
a	O
weighted	B-Application
list	I-Application
.	O
</s>
<s>
These	O
collocates	B-General_Concept
are	O
formatted	O
to	O
show	O
frequency	O
(	O
as	O
size	O
)	O
as	O
well	O
as	O
collocational	O
strength	O
(	O
as	O
brightness	O
)	O
.	O
</s>
<s>
Tag	B-Application
clouds	I-Application
have	O
been	O
subject	O
of	O
investigation	O
in	O
several	O
usability	O
studies	O
.	O
</s>
<s>
Tag	B-General_Concept
size	O
:	O
Large	O
tags	B-General_Concept
attract	O
more	O
user	O
attention	O
than	O
small	O
tags	B-General_Concept
(	O
effect	O
influenced	O
by	O
further	O
properties	O
,	O
e.g.	O
,	O
number	O
of	O
characters	O
,	O
position	O
,	O
neighboring	O
tags	B-General_Concept
)	O
.	O
</s>
<s>
Scanning	O
:	O
Users	O
scan	O
rather	O
than	O
read	O
tag	B-Application
clouds	I-Application
.	O
</s>
<s>
Centering	O
:	O
Tags	B-General_Concept
in	O
the	O
middle	O
of	O
the	O
cloud	O
attract	O
more	O
user	O
attention	O
than	O
tags	B-General_Concept
near	O
the	O
borders	O
(	O
effect	O
influenced	O
by	O
layout	O
)	O
.	O
</s>
<s>
Exploration	O
:	O
Tag	B-Application
clouds	I-Application
provide	O
suboptimal	O
support	O
when	O
searching	O
for	O
specific	O
tags	B-General_Concept
(	O
if	O
these	O
do	O
not	O
have	O
a	O
very	O
large	O
font	O
size	O
)	O
.	O
</s>
<s>
compared	O
how	O
human	O
reading	O
performance	O
differs	O
from	O
traditional	O
tag	B-Application
clouds	I-Application
that	O
map	O
numeric	O
values	O
to	O
the	O
size	O
of	O
the	O
font	O
and	O
alternative	O
designs	O
that	O
uses	O
for	O
example	O
color	O
or	O
additional	O
shapes	O
like	O
circle	O
and	O
bars	O
.	O
</s>
<s>
The	O
performance	O
depends	O
on	O
the	O
task	O
,	O
simple	O
tasks	O
like	O
finding	O
a	O
word	O
are	O
highly	O
affected	O
by	O
the	O
design	O
choice	O
,	O
however	O
the	O
effect	O
on	O
tasks	O
like	O
identify	O
the	O
topic	O
of	O
a	O
tag	B-Application
cloud	I-Application
is	O
much	O
smaller	O
.	O
</s>
<s>
In	O
principle	O
,	O
the	O
font	O
size	O
of	O
a	O
tag	B-General_Concept
in	O
a	O
tag	B-Application
cloud	I-Application
is	O
determined	O
by	O
its	O
incidence	O
.	O
</s>
<s>
For	O
a	O
word	B-Application
cloud	I-Application
of	O
categories	O
like	O
weblogs	O
,	O
frequency	O
,	O
for	O
example	O
,	O
corresponds	O
to	O
the	O
number	O
of	O
weblog	O
entries	O
that	O
are	O
assigned	O
to	O
a	O
category	O
.	O
</s>
<s>
Implementations	O
of	O
tag	B-Application
clouds	I-Application
also	O
include	O
text	O
parsing	O
and	O
filtering	O
out	O
unhelpful	O
tags	B-General_Concept
such	O
as	O
common	O
words	O
,	O
numbers	O
,	O
and	O
punctuation	O
.	O
</s>
<s>
There	O
are	O
also	O
websites	O
creating	O
artificially	O
or	O
randomly	O
weighted	O
tag	B-Application
clouds	I-Application
,	O
for	O
advertising	O
,	O
or	O
for	O
humorous	O
results	O
.	O
</s>
