If you type in "object-oriented" to search for past posts on this
interesting subject (http://www.optimlator.com ), you may find new
interesting ideas. Also, in response to Geoff McDonnell, there is a link for
"CAS and AL" in the "System Dynamics" pull-down menu (at the above site)
with many useful links. Hope this info will help.
Linux and open source movement became powerful because of the enormous use
people found for the OS/software (and now even corporations such as IBM and
other major vendors who have started offering Linux as options) and because
of the non-academic but very efficient peer-review system of quality control
built-in in this movement. SD is not so popular and immediately useful as to
garner that kind of popular support and peer-reviewed quality control. Lack
of standards is another problem. Besides, how many consultants will put
their bags of tricks out into the open in this fiercely competitive market -
academics are a different breed, however, but their solutions can be
ivory-tower variety at times.
I am skeptical of the Open Source idea in SD, though who knows - Linux
started gaining popularity only recently compared to other OSs. If there are
die-hard passionate people in SD, willing to slog it out for free, it can
happen here too. But I wouldnt bet on it, at least for now.
Maybe the movement should start with starving graduate students, as the
Linux movement did :>)
Jaideep Mukherjee, Ph. D.
jaideep@optimlator.com
LINUX equivalent for modelling
-
"J Mukherjee"
- Junior Member
- Posts: 6
- Joined: Fri Mar 29, 2002 3:39 am
-
Bill Harris
- Senior Member
- Posts: 75
- Joined: Fri Mar 29, 2002 3:39 am
LINUX equivalent for modelling
I lost the beginnings of this thread--whether the focus is on free SD
software or SD software on Linux. At any rate, Paul Fishwicks simpack
includes some SD capability, although you might only like it if you find
DYNAMO nice but too GUIfied and far from the metal for your tastes. As
its a C framework to be compiled, it should run on any machine for
which you can compile C (or C++; it may be that only early versions were
in C, but I think Ive run some of the C "package" on an old Apple
IIGS). I think he once had some grad students working on an X Window
System based SD package, but I dont know how far it got. See
http://www.cise.ufl.edu/~fishwick/simpack/simpack.html.
Theres also W. Hubfelds Dynasys. When I looked at it, it seemed a bit
like an early iThink. AFAIK, its quite inexpensive but not free.
Neither one are free in the GPL sense, but they may help some people.
Check the software and the licensing.
Bill
From: Bill Harris <bill_harris@facilitatedsystems.com>
--
Bill Harris 3217 102nd Place SE
Facilitated Systems Everett, WA 98208 USA
http://facilitatedsystems.com/ phone: +1 425 337-5541
software or SD software on Linux. At any rate, Paul Fishwicks simpack
includes some SD capability, although you might only like it if you find
DYNAMO nice but too GUIfied and far from the metal for your tastes. As
its a C framework to be compiled, it should run on any machine for
which you can compile C (or C++; it may be that only early versions were
in C, but I think Ive run some of the C "package" on an old Apple
IIGS). I think he once had some grad students working on an X Window
System based SD package, but I dont know how far it got. See
http://www.cise.ufl.edu/~fishwick/simpack/simpack.html.
Theres also W. Hubfelds Dynasys. When I looked at it, it seemed a bit
like an early iThink. AFAIK, its quite inexpensive but not free.
Neither one are free in the GPL sense, but they may help some people.
Check the software and the licensing.
Bill
From: Bill Harris <bill_harris@facilitatedsystems.com>
--
Bill Harris 3217 102nd Place SE
Facilitated Systems Everett, WA 98208 USA
http://facilitatedsystems.com/ phone: +1 425 337-5541
-
Roland Schiefer
- Newbie
- Posts: 1
- Joined: Fri Mar 29, 2002 3:39 am
LINUX equivalent for modelling
It was argued that SD is a specialised tool, like a hammer, and that one
would not gain by combining it with another specialised tool, say, a
screwdriver. Through my own professional experience I got a different view.
Usually there is a customer, such as a company or a government organisation,
who wants a solution and does not care much about the tools used to produce
it. In building terms they are not looking for a hammer, nor for a
specialist in using hammers. They are looking for the equivalent of a
handyman to make alterations to the THIS IS SPAM.
A real handyman has his trusted toolbox with hammer, screwdriver, power
drill, jigsaw, etc. He uses them all, as required, to do the job. In
modelling this is presently not the case. There are the equivalents of
hammer experts (SD), screwdriver experts (discrete simulation), etc. To
alter a THIS IS SPAM one would have to employ a team of such experts plus the
managers required to coordinate them. This is prohibitively expensive. If
the job is of a kind that a hammer or a screwdriver expert can handle it
alone, a contract may be given. If this is not the case, the customer may
solve his problems in another way. I assume for this reason most potential
modelling contracts are never awarded.
Often there are no suitable packages available. In addition there is also
the problem of cost. Many packets that might be useful for a certain
application are prohibitively expensive, especially if several of them would
have to be used in one project. It is then often cheaper to build a package
tailored to the job. I am quite convinced that my professional experience is
not unique. Here are a few examples.
* For my masters thesis I needed an SD package. Then (1977) we had only
DYNAMO on the university mainframe. The integration (linear) did not do the
job, so I developed my own package, using the Runge-Kutta method. I needed a
non-linear solver as well, so I developed one.
* When I simulated gas transport in divers during decompression, I used
another self-made simulation environment
* To model financial and environmental aspects of energy supply systems I
wrote yet another modelling environment. It focussed on process chains and
ignored feedback structures, but would they have been available with little
effort, I would have used them.
Imagine similar efforts of numerous other modellers and developers would not
be spent in re-building the same basic tools with slight modifications.
Imagine these efforts would be spent contributing to an Open Modelling
System (OMS). Once developed, components could be re-used with little
additional effort, and the development time saved could be spent on
understanding the system better. Alternatively, inventive minds could spend
that time building new types of components. It seems obvious that such a
system would soon exceed the capabilities of any commercially available
system today.
In order to make use of an existing structure, modellers would have to
strive to make their special requirements fit into the existing structure
and to minimise the need for additional components (which they have to
produce themselves). This would encourage the development of an integrated
modelling concept in an evolutionary manner.
To make use of the considerable intellectual capacity at educational
institutions, OMS would have to be free. Just like LINUX. Somebody would
have to start it off by defining the framework and the standards, and by
creating a useful kernel that makes it worthwhile for others to start
considering OMS for real work. As for the administration of such an effort,
much could be learned from the LINUX movement.
Some questions in this context are: Is the OMS suggestion sensible at all?
Would you use OMS? Can you see yourself contributing functional modules to
OMS? Can you imagine an agreement on the required standards? Who should
produce the kernel? Who might sponsor such an effort?
Roland Schiefer
Technical Consultant
schiefer@iafrica.com
would not gain by combining it with another specialised tool, say, a
screwdriver. Through my own professional experience I got a different view.
Usually there is a customer, such as a company or a government organisation,
who wants a solution and does not care much about the tools used to produce
it. In building terms they are not looking for a hammer, nor for a
specialist in using hammers. They are looking for the equivalent of a
handyman to make alterations to the THIS IS SPAM.
A real handyman has his trusted toolbox with hammer, screwdriver, power
drill, jigsaw, etc. He uses them all, as required, to do the job. In
modelling this is presently not the case. There are the equivalents of
hammer experts (SD), screwdriver experts (discrete simulation), etc. To
alter a THIS IS SPAM one would have to employ a team of such experts plus the
managers required to coordinate them. This is prohibitively expensive. If
the job is of a kind that a hammer or a screwdriver expert can handle it
alone, a contract may be given. If this is not the case, the customer may
solve his problems in another way. I assume for this reason most potential
modelling contracts are never awarded.
Often there are no suitable packages available. In addition there is also
the problem of cost. Many packets that might be useful for a certain
application are prohibitively expensive, especially if several of them would
have to be used in one project. It is then often cheaper to build a package
tailored to the job. I am quite convinced that my professional experience is
not unique. Here are a few examples.
* For my masters thesis I needed an SD package. Then (1977) we had only
DYNAMO on the university mainframe. The integration (linear) did not do the
job, so I developed my own package, using the Runge-Kutta method. I needed a
non-linear solver as well, so I developed one.
* When I simulated gas transport in divers during decompression, I used
another self-made simulation environment
* To model financial and environmental aspects of energy supply systems I
wrote yet another modelling environment. It focussed on process chains and
ignored feedback structures, but would they have been available with little
effort, I would have used them.
Imagine similar efforts of numerous other modellers and developers would not
be spent in re-building the same basic tools with slight modifications.
Imagine these efforts would be spent contributing to an Open Modelling
System (OMS). Once developed, components could be re-used with little
additional effort, and the development time saved could be spent on
understanding the system better. Alternatively, inventive minds could spend
that time building new types of components. It seems obvious that such a
system would soon exceed the capabilities of any commercially available
system today.
In order to make use of an existing structure, modellers would have to
strive to make their special requirements fit into the existing structure
and to minimise the need for additional components (which they have to
produce themselves). This would encourage the development of an integrated
modelling concept in an evolutionary manner.
To make use of the considerable intellectual capacity at educational
institutions, OMS would have to be free. Just like LINUX. Somebody would
have to start it off by defining the framework and the standards, and by
creating a useful kernel that makes it worthwhile for others to start
considering OMS for real work. As for the administration of such an effort,
much could be learned from the LINUX movement.
Some questions in this context are: Is the OMS suggestion sensible at all?
Would you use OMS? Can you see yourself contributing functional modules to
OMS? Can you imagine an agreement on the required standards? Who should
produce the kernel? Who might sponsor such an effort?
Roland Schiefer
Technical Consultant
schiefer@iafrica.com
-
Alexander Lubyansky
- Junior Member
- Posts: 2
- Joined: Fri Mar 29, 2002 3:39 am
LINUX equivalent for modelling
I am not sure how "open" it is, but I found a tool called "A Modeling
Environment" now renamed "Simile"
http://helios.bto.ed.ac.uk/ierm/ame/
is the address of it. It seems to be a modelling environment developed by
the University of Edinburgh, in the UK.
I just found it recently, but from the looks of it, the software has a
system dynamics modelling environment, as well as some other code and
visualization related abilities. It looks less user-friendly to use and
seems to require more knowledge about programming and computers than the
current commercial titles.
It is free and freely downloadable, so it is free as in free beer. It is
also available in Windows 9x/NT as well as Linux. The source code is
downloadable for the linux version, so I am making a guess that AME is
open-source.
I do not know if this is the Open Modelling System that is under discussion,
but it really looks as if it is akin to such a thing.
I say, hurray for open/multiplatform SD modelling software! I do not think
that anyone will see ithink/Stella, Powersim, or Vensim (the "Big Three") on
linux anytime in the near future, plus some of us do not wish to, or cannot
pay a hundred dollars or more for SD software, even if the free stuff lacks
some of the functionality, support, and ease-of-use of the commercial
software.
Again, I just found this AME, so my information may be flawed, thus have
mercy on me.
From: Alexander Lubyansky <driedcow@email.com>
Sasha Lubyansky
Environment" now renamed "Simile"
http://helios.bto.ed.ac.uk/ierm/ame/
is the address of it. It seems to be a modelling environment developed by
the University of Edinburgh, in the UK.
I just found it recently, but from the looks of it, the software has a
system dynamics modelling environment, as well as some other code and
visualization related abilities. It looks less user-friendly to use and
seems to require more knowledge about programming and computers than the
current commercial titles.
It is free and freely downloadable, so it is free as in free beer. It is
also available in Windows 9x/NT as well as Linux. The source code is
downloadable for the linux version, so I am making a guess that AME is
open-source.
I do not know if this is the Open Modelling System that is under discussion,
but it really looks as if it is akin to such a thing.
I say, hurray for open/multiplatform SD modelling software! I do not think
that anyone will see ithink/Stella, Powersim, or Vensim (the "Big Three") on
linux anytime in the near future, plus some of us do not wish to, or cannot
pay a hundred dollars or more for SD software, even if the free stuff lacks
some of the functionality, support, and ease-of-use of the commercial
software.
Again, I just found this AME, so my information may be flawed, thus have
mercy on me.
From: Alexander Lubyansky <driedcow@email.com>
Sasha Lubyansky