1.4. Wh at Is Dynamic Modeling?
9
off the coast of New England (a well-studied region for decades), the barndoor skate (Raj a laevis) is in danger of becoming extinct (Casey and Myers
1999), The barnd oor skate, with a wingspan of 3 feet and a total length of
5 feet, is one of world's largest marine rays. But it isn't fished for food . It
lives we ll out of sight, and out of mind , of hum an society. Fishing activityprimarily with mobile fishing gear-has inadve rtently brought the barndoor skate to the edge of extinction, and for a long time nobody realized it.
Its plight ep itomizes that of many troubled marine creatures and systems
around the wo rld.
Land and water are differen t. The primary difference between marine
and terrestrial environments has been described as one of medium-air
versus water. The buoyancy of organisms in the respective medium, the
rate of medium flow , and the thermal stratification within each medium all
contribute to the developm ent of very different functional structures of organisms (Iamieson and Levings 1998). Conducting research in the marine
environment presents many challenges not encountered on land. Individual
researchers are often limited in their ability to observe organisms in their
environment, either by maximum bottom times for SCUBA or by the expense of depl oying manned submersibles and remotely ope rated vehicles
(ROYs). In many instances, marine science- literally-only skims the surface and often provides fragmentary insights into a vast system. Dynamic
modeling can help put the pieces of the marine pu zzle together and can
provide researchers the opportu nity to explore the implications of their
knowledge and refine research questions prior to field experiments. Simple, yet powerful, models of a given system or subsystem can provide important information to scientists and managers alike with respect to future
trajectories of a system's develop ment under a variety of conditions.
1.4. What Is Dynamic Modeling?
Dynamic modeling is a process of extending our knowledge, and the computer is only a means towards this end. Modeling with the graphical programming language STELLA is a process that evokes the most easily accessible form of symbolic understanding by humans, the use of icons. As you
will find throughout the text, the classification of variables is quite simple
and the resulting icons associated with them are appro priate for capturing
all the parts that influe nce a system's behavior. An expe rienced STELLA
modeler literally sees and und erstands the dynamic process through the
arrangement of these icons. This is part of what we mean by the art of dynamic modeling. This art can be practiced by anyone with knowledge of
basic mathematics and the ability to use a personal computer.
The best way to become fluent in the use of the programming langu age
is to use the icons rep eatedly in many different applications. Our book contains a set of models of marine biological systems that use a common tool
9
off the coast of New England (a well-studied region for decades), the barndoor skate (Raj a laevis) is in danger of becoming extinct (Casey and Myers
1999), The barnd oor skate, with a wingspan of 3 feet and a total length of
5 feet, is one of world's largest marine rays. But it isn't fished for food . It
lives we ll out of sight, and out of mind , of hum an society. Fishing activityprimarily with mobile fishing gear-has inadve rtently brought the barndoor skate to the edge of extinction, and for a long time nobody realized it.
Its plight ep itomizes that of many troubled marine creatures and systems
around the wo rld.
Land and water are differen t. The primary difference between marine
and terrestrial environments has been described as one of medium-air
versus water. The buoyancy of organisms in the respective medium, the
rate of medium flow , and the thermal stratification within each medium all
contribute to the developm ent of very different functional structures of organisms (Iamieson and Levings 1998). Conducting research in the marine
environment presents many challenges not encountered on land. Individual
researchers are often limited in their ability to observe organisms in their
environment, either by maximum bottom times for SCUBA or by the expense of depl oying manned submersibles and remotely ope rated vehicles
(ROYs). In many instances, marine science- literally-only skims the surface and often provides fragmentary insights into a vast system. Dynamic
modeling can help put the pieces of the marine pu zzle together and can
provide researchers the opportu nity to explore the implications of their
knowledge and refine research questions prior to field experiments. Simple, yet powerful, models of a given system or subsystem can provide important information to scientists and managers alike with respect to future
trajectories of a system's develop ment under a variety of conditions.
1.4. What Is Dynamic Modeling?
Dynamic modeling is a process of extending our knowledge, and the computer is only a means towards this end. Modeling with the graphical programming language STELLA is a process that evokes the most easily accessible form of symbolic understanding by humans, the use of icons. As you
will find throughout the text, the classification of variables is quite simple
and the resulting icons associated with them are appro priate for capturing
all the parts that influe nce a system's behavior. An expe rienced STELLA
modeler literally sees and und erstands the dynamic process through the
arrangement of these icons. This is part of what we mean by the art of dynamic modeling. This art can be practiced by anyone with knowledge of
basic mathematics and the ability to use a personal computer.
The best way to become fluent in the use of the programming langu age
is to use the icons rep eatedly in many different applications. Our book contains a set of models of marine biological systems that use a common tool