Dr. Thomas P. Maxwell
Maryland Institute for Ecological Economics
voice: (410)-326-7388, FAX: (410)-326-7354.
email: maxwell@cbl.umces.edu
Selected Papers
Developing Understanding of Ecological Economic Systems
Thomas Maxwell, Robert Costanza, Mattais Ruth, and Alexey Voinov
This paper, presented at the International Conference on Complex Systems in
Nashua, NH (2000), emphasizes the collaborative, consensus-building phases of
the modeling process.
Download: postscript.
Collaborative Modular Modeling Of Environmental Systems
Thomas Maxwell and Ferdinando Villa
Soon to be published as book chapter.
ABSTRACT
We believe that effectively managing human affairs through the next century
will require extremely complex and reliable computer models. Programs
such as NASA's Mission to Planet Earth (MTPE) (NASA, 1996) augmented by the
development of the Open Geodata Interoperability Specification (OGIS) by the
Open GIS Consortium (OGIS, 1996) have paved the way by providing an open
framework for universal geographic data access and processing. Scientists
hope that as the data from Mission to Planet Earth and other programs are
integrated into these models, it will be possible to understand better the
roles of particular aspects of the global environment, as well as to predict
how the environment will change over time. Building accurate models is a
complex task. NASA and other agencies involved in global change studies hope
that through a combination of better global data from space observations,
faster computers, and improved modeling techniques, global change data can be
turned into information relevant for making policy (NASA, 1996).
The crucial next step in this research plan is the development of an open
framework to support collaborative dynamic modeling.
This chapter describes an ongoing program to develop this infrastructure for
open geographic modeling. We are establishing a Modeling Collaboratory,
i.e. a hardware and software laboratory that can be used for the exploration of
collaborative modeling techniques and the development of spatial models, as
well as transparent access to high performance computing facilities. We
expect that this infrastructure will open the simulation arena to a much wider
set of participants, and facilitate the application of computer modeling to the
study and management of natural systems. Our vision is to harness
advanced information technologies to promote science-based, collaborative
exploration of natural system dynamics by diverse
stakeholders/managers/students, and thereby help strengthen environmental
awareness, planning, and decision-making for conservation and sustainable
development of natural resources.
Download: postscript.
A Parsi-Model Approach to Modular Simulation
Thomas Maxwell (1999)
Environmental Modeling and Software, v. 14, pp. 511-517.
ABSTRACT
The development of complex models can be greatly facilitated by the utilization
of libraries of reusable model components. In this paper we describe an
object-oriented module specification formalism (MSF) for implementing
archivable modules in support of continuous spatial modeling. This
declarative formalism provides the high level of abstraction necessary for
maximum generality, provides enough detail to allow a dynamic simulation to be
generated automatically, and avoids the "hard-coded" implementation of
space-time dynamics that makes procedural specifications of limited usefulness
for specifying archivable modules. A set of these MSF modules can
be hierarchically linked to create a parsimonious model specification, or
"parsi-model". The parsi-model exists within the context of a modeling
environment ( an integrated set of software tools which provide the computer
services necessary for simulation development and execution ), which can offer
simulation services that are not possible in a loosely-coupled "federated"
environment, such as graphical module development and configuration, automatic
differentiation of model equations, run-time visualization of the data and
dynamics of any variable in the simulation, transparent distributed computing
within each module, and fully configurable space-time representations. We
believe this approach has great potential for bringing the power of modular
model development into the collaborative simulation arena.
Download: postscript.
An Open Geographic Modeling Environment
Thomas Maxwell and Robert Costanza (1997)
Simulation Journal, v. 68, no. 3 pp. 175-185
ABSTRACT
Developing the complex computer models that are necessary for effectively
managing human affairs through the next century requires new infrastructure
supporting high performance collaborative modeling. In this paper we
describe our Open Georgaphic Modeling Environment, which supports 1) modular,
hierarchical model construction and archiving/linking of simulation modules, 2)
graphical, icon-based model construction, 3) transparent distributed computing,
and 4) integrating multiple space-time representations. This environment,
which transparently links icon-based modeling environments with advanced
computing resources, allows users to develop models in a user-friendly,
graphical environment, requiring very little knowledge of computers or computer
programming. Automatic code generators construct spatial simulations and
enable distributed processing over a network of parallel and serial computers,
allowing transparent access to state-of-the-art computing facilities. The
modeling environment imposes the constraints of modularity and hierarchy in
program design, and supports archiving of reusable modules in our Modular
Modeling Language (MML). An associated library of "module wrappers" will
facilitate the incorporation of legacy simulation models into the
environment. It is hoped that this type of infrastructure will open the
simulation arena to a much wider set of participants, and facilitate the
application of computer modeling to the study of complex multi-scale processes
in support of policy making on many levels.
Download: postscript.