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WLinkIt
is representative of a category of computer based modelling systems
called semi-quantitative systems. The system can be used to represent
causal relationships between objects and/or events of a certain
domain. The vocabulary used in its environment tries to correspond
well to intuitive or common-sense ways of talking about systems.
The construction of a model with WLinkIt is made through the use
of a direct-manipulation interface using a graph metaphor to define
the objects and relationship of a certain model. In most cases
these objects can be used by the modeller to represent some aspects
of the world to be modelled such as the level of pollution of
a city, its main causes and its consequence on the health of the
population of that city .
The central idea with this style of interface is to try to focus
the attention of the user on the objects and actions of interest,
replacing, for instance, a command-based interface where the operations
are made through a more artificial and indirect process.
To create a model with WLinkIt, the user has to define the variables
and relationships and attach to them some characteristics that
reflect the functional aspects of the objects and events being
modelled. The system, in its turn, is responsible for running
the model. In order to do so, it executes two steps: First it
has to choose a set of mathematical equations (always hidden
from the user) - based on the characteristics of the variables
and relationships already created - that will control the behaviour
of the model. Second, it makes the model evolve over time through
the calculation and iteration of these equations. During this
process of running the model, the user receives visual feedback
from the system, seeing changes in some physical aspects of the
objects on the screen.
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