<s>
Whereas	O
words	O
are	O
still	O
assumed	O
to	O
be	O
exchangeable	O
,	O
in	O
a	O
dynamic	B-General_Concept
topic	I-General_Concept
model	I-General_Concept
the	O
order	O
of	O
the	O
documents	O
plays	O
a	O
fundamental	O
role	O
.	O
</s>
<s>
Similarly	O
to	O
LDA	O
and	O
pLSA	B-General_Concept
,	O
in	O
a	O
dynamic	B-General_Concept
topic	I-General_Concept
model	I-General_Concept
,	O
each	O
document	O
is	O
viewed	O
as	O
a	O
mixture	O
of	O
unobserved	O
topics	O
.	O
</s>
<s>
Even	O
though	O
multinomial	O
distributions	O
are	O
usually	O
written	O
in	O
terms	O
of	O
the	O
mean	O
parameters	O
,	O
representing	O
them	O
in	O
terms	O
of	O
the	O
natural	O
parameters	O
is	O
better	O
in	O
the	O
context	O
of	O
dynamic	B-General_Concept
topic	I-General_Concept
models	I-General_Concept
.	O
</s>
<s>
In	O
the	O
dynamic	B-General_Concept
topic	I-General_Concept
model	I-General_Concept
,	O
only	O
is	O
observable	O
.	O
</s>
<s>
Blei	O
and	O
Lafferty	O
argue	O
that	O
applying	O
Gibbs	B-Algorithm
sampling	I-Algorithm
to	O
do	O
inference	O
in	O
this	O
model	O
is	O
more	O
difficult	O
than	O
in	O
static	O
models	O
,	O
due	O
to	O
the	O
nonconjugacy	O
of	O
the	O
Gaussian	O
and	O
multinomial	O
distributions	O
.	O
</s>
<s>
They	O
propose	O
the	O
use	O
of	O
variational	B-Algorithm
methods	I-Algorithm
,	O
in	O
particular	O
,	O
the	O
Variational	O
Kalman	O
Filtering	O
and	O
the	O
Variational	O
Wavelet	O
Regression	O
.	O
</s>
<s>
In	O
the	O
original	O
paper	O
,	O
a	O
dynamic	B-General_Concept
topic	I-General_Concept
model	I-General_Concept
is	O
applied	O
to	O
the	O
corpus	O
of	O
Science	O
articles	O
published	O
between	O
1881	O
and	O
1999	O
aiming	O
to	O
show	O
that	O
this	O
method	O
can	O
be	O
used	O
to	O
analyze	O
the	O
trends	O
of	O
word	O
usage	O
inside	O
topics	O
.	O
</s>
<s>
A	O
continuous	O
dynamic	B-General_Concept
topic	I-General_Concept
model	I-General_Concept
was	O
developed	O
by	O
Wang	O
et	O
al	O
.	O
</s>
<s>
Going	O
beyond	O
text	O
documents	O
,	O
dynamic	B-General_Concept
topic	I-General_Concept
models	I-General_Concept
were	O
used	O
to	O
study	O
musical	O
influence	O
,	O
by	O
learning	O
musical	O
topics	O
and	O
how	O
they	O
evolve	O
in	O
recent	O
history	O
.	O
</s>
