<s>
VisTrails	B-Language
is	O
a	O
scientific	B-Application
workflow	I-Application
management	I-Application
system	I-Application
developed	O
at	O
the	O
Scientific	O
Computing	O
and	O
Imaging	O
Institute	O
at	O
the	O
University	O
of	O
Utah	O
that	O
provides	O
support	O
for	O
data	O
exploration	O
and	O
visualization	B-Application
.	O
</s>
<s>
It	O
is	O
written	O
in	O
Python	B-Language
and	O
employs	O
Qt	B-Language
via	O
PyQt	B-Language
bindings	O
.	O
</s>
<s>
The	O
pre-compiled	O
versions	O
for	O
Windows	B-Application
,	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
,	O
and	O
Linux	B-Application
come	O
with	O
an	O
installer	O
and	O
several	O
packages	O
,	O
including	O
VTK	B-Language
,	O
matplotlib	B-Language
,	O
and	O
ImageMagick	B-Language
.	O
</s>
<s>
VisTrails	B-Language
also	O
supports	O
user-defined	O
packages	O
.	O
</s>
<s>
It	O
combines	O
features	O
of	O
workflow	B-Operating_System
and	O
visualization	B-Application
systems	O
.	O
</s>
<s>
workflow	B-Operating_System
systems	O
,	O
it	O
allows	O
the	O
combination	O
of	O
loosely	O
coupled	O
resources	O
,	O
specialized	O
libraries	O
,	O
</s>
<s>
Scalable	O
derivation	O
of	O
data	O
products	O
,	O
parameter	O
exploration	O
,	O
multi-view	O
and	O
comparative	O
visualization	B-Application
.	O
</s>
<s>
VisTrails	B-Language
is	O
the	O
result	O
of	O
a	O
collaborative	O
effort	O
between	O
computer	O
scientists	O
Cláudio	O
Silva	O
and	O
Juliana	O
Freire	O
.	O
</s>
<s>
Although	O
the	O
first	O
prototypes	O
were	O
implemented	O
in	O
C++	B-Language
,	O
the	O
current	O
version	O
of	O
VisTrails	B-Language
is	O
written	O
in	O
Python	B-Language
.	O
</s>
<s>
A	O
common	O
use	O
for	O
VisTrails	B-Language
is	O
scientific	B-Application
visualization	I-Application
.	O
</s>
<s>
Visualizations	B-Application
generated	O
as	O
part	O
of	O
a	O
workflow	B-Operating_System
are	O
rendered	O
in	O
a	O
spreadsheet-style	O
interface	O
,	O
allowing	O
multiple	O
visualizations	B-Application
from	O
different	O
versions	O
of	O
a	O
workflow	B-Operating_System
to	O
be	O
viewed	O
and	O
compared	O
simultaneously	O
.	O
</s>
<s>
The	O
VisTrails	B-Language
spreadsheet	B-Application
currently	O
supports	O
VTK	B-Language
and	O
HTML	B-Language
rendering	O
.	O
</s>
<s>
VisTrails	B-Language
supports	O
four	O
basic	O
modes	B-General_Concept
,	O
or	O
views	O
.	O
</s>
<s>
Each	O
view	O
interacts	O
with	O
the	O
underlying	O
workflow	B-Operating_System
in	O
a	O
different	O
way	O
.	O
</s>
<s>
The	O
Pipeline	B-Operating_System
view	O
lets	O
the	O
user	O
create	O
,	O
view	O
and	O
edit	O
a	O
visual	O
pipeline	B-Operating_System
of	O
a	O
workflow	B-Operating_System
.	O
</s>
<s>
The	O
pipelines	B-Operating_System
are	O
typically	O
rendered	O
from	O
top	O
to	O
bottom	O
,	O
with	O
each	O
module	O
's	O
output	O
connecting	O
to	O
the	O
input	O
of	O
the	O
module(s )	O
below	O
it	O
.	O
</s>
<s>
The	O
History	O
view	O
displays	O
a	O
tree	B-Data_Structure
structure	I-Data_Structure
representing	O
the	O
various	O
versions	O
of	O
the	O
pipeline	B-Operating_System
.	O
</s>
<s>
Each	O
time	O
a	O
change	O
is	O
made	O
in	O
the	O
Pipeline	B-Operating_System
view	O
,	O
a	O
new	O
node	O
is	O
added	O
to	O
the	O
version	O
tree	O
in	O
the	O
History	O
view	O
.	O
</s>
<s>
To	O
conserve	O
space	O
,	O
VisTrails	B-Language
does	O
not	O
render	O
a	O
node	O
unless	O
it	O
is	O
a	O
root	O
or	O
leaf	O
node	O
or	O
has	O
a	O
tag	O
.	O
</s>
<s>
The	O
Query	O
view	O
is	O
similar	O
in	O
appearance	O
to	O
the	O
Pipeline	B-Operating_System
view	O
.	O
</s>
<s>
Here	O
,	O
the	O
user	O
constructs	O
partial	O
pipelines	B-Operating_System
.	O
</s>
<s>
When	O
the	O
query	O
is	O
executed	O
,	O
VisTrails	B-Language
identifies	O
the	O
pipeline	B-Operating_System
versions	O
which	O
contain	O
the	O
specified	O
partial	O
pipeline	B-Operating_System
.	O
</s>
<s>
This	O
is	O
analogous	O
to	O
the	O
Query	B-Application
By	I-Application
Example	I-Application
method	O
of	O
performing	O
database	O
queries	O
.	O
</s>
<s>
The	O
Exploration	O
view	O
automates	O
the	O
process	O
of	O
creating	O
several	O
workflow	B-Operating_System
pipelines	B-Operating_System
that	O
differ	O
only	O
by	O
a	O
few	O
parameter	O
values	O
.	O
</s>
<s>
In	O
2007	O
,	O
the	O
University	O
of	O
Utah	O
formed	O
VisTrails	B-Language
,	O
Inc.	O
,	O
a	O
spinoff	O
company	O
intended	O
to	O
commercialize	O
VisTrails	B-Language
technology	O
.	O
</s>
<s>
Development	O
for	O
the	O
free	O
version	O
of	O
VisTrails	B-Language
is	O
currently	O
funded	O
by	O
the	O
University	O
of	O
Utah	O
and	O
VisTrails	B-Language
,	O
Inc	O
.	O
</s>
<s>
The	O
company	O
's	O
first	O
product	O
is	O
a	O
plugin	O
for	O
the	O
3D	O
modeling	O
software	O
Maya	B-Language
.	O
</s>
<s>
While	O
the	O
main	O
VisTrails	B-Language
distribution	O
is	O
free	B-Application
software	I-Application
,	O
the	O
VisTrails	B-Language
plugin	O
for	O
Maya	B-Language
is	O
distributed	O
under	O
a	O
closed-source/proprietary	B-Application
license	I-Application
.	O
</s>
