Environmental Engineering Reference
In-Depth Information
(Foth
et al
., 2009). The emerging web-based technologies have
also enabled a new level of synthesis of a heterogeneous geospatial
information and lead to a better understanding of urban forms
and processes at multiple scales (http://www.londonprofiler.org).
By looking at urban modeling efforts through a metaphorical
perspective, we can better understand what Couclelis (1984)
called the ''prior structure'' of the models. As the driving
metaphors in urban models, regardless whether you are drawn
from mathematics, physics, biology or computational science,
some ''prior structure'' is already embedded in the conceptual
foundation of every model. Precisely because of the baggage with
various metaphors, modelers and critics alike have called for
alternative grounding of our modeling efforts. O'Kelly (2004)
called for a move from crude physical or biological metaphors
into grounding our modeling efforts more in social/behavioral
sciences. The difficulty is that some of the leading theories in social
and behavior sciences are also embedded in physical or biologi-
cal metaphors (Mirowski, 1991; Levine, 1995; McCloskey, 1995;
Gaziano, 1999; Phillips, 2007). Social scientists have never ceased
their efforts to ground their work in various natural sciences
(Phillips, 1992). As Solow (2005) pointed out, economics got the
way it is primarily due to influences from natural sciences, espe-
cially physics and biology. In this context, what I believe urban
modelers need to realize is that whatever insights we may gain
from understanding the modeling efforts do not necessarily rep-
resent (much less correspond to, as most urban modelers seem
to believe) a better match to the external urban reality, but will
reflect primarily the internal logics of the metaphor employed.
In other words, urban modeling results are not necessarily a
testimony to the empirical robustness of what is physically inside
cities, but primarily to the power of the various metaphors in
urban modelers' imagination. In other words, urban modeling is
constitutive, not simply reflective.
Previous reviews on urban modeling efforts have concen-
trated primarily on the technical and methodological details
without probing deeply the underlying metaphors embedded in
the diverse modeling efforts. What we traditionally consider as
progress is, in fact, nothing but a shift in the driving metaphors
we used for conceptualization of cities. In this context, what we
should recognize is the process whereby meaning is produced
from metaphor to metaphor, rather than, as it was often assumed
by urban modelers, between model and the world. We need
not only to check the validity of our models from the technical
perspective in terms of data accuracy and consistency with the
previous data (Yeh and Li, 2006), but also, and perhaps more
importantly, to scrutinize the driving conceptual metaphors
deeply embedded in the models. Only then can we weave the
insights gained from the urban modeling efforts with other urban
narratives (Finnegan, 1998) to have a more sensible and sensitive
urban life.
26.4
Models, metaphors,
and themeaning of
progress: further
discussions
As an organizing framework, Pepper's world hypotheses
undoubtedly can help us understand the diverse urban modeling
efforts in a more systematic manner. But I must emphasize
that although the four traditions and their dominant/driving
metaphors can be identified, urban modelers seldom rely on one
metaphor exclusively; instead, most have used a mixture of mul-
tiple metaphors or modeling traditions. For example, Michael
Batty, who has been active in the field for over four decades,
has contributed to all four modeling traditions in his work.
Most of Batty's work has been motivated by a combination of
mathematical, physical, biological, and computation metaphors.
Alan Wilson, the leading urban modeler following the social
physics tradition in the 1960s and 1970s, has invoked DNA,
genetic, and ecological analogies in his recent work (Wilson,
2008), although he still relies primarily on techniques from math
and physics to implement and operationalize his models.
Each modeling tradition is also conceptually and method-
ologically permeable. In morphological studies linked to the
concept of fractal cities, urban development has been designed to
follow the diffusion-limited aggregation (DLA) model of physics,
which generates tree-like clusters of population around some
focal points. Modeling and simulating individual events are often
relying on CA/AB models, whereas the new field-based time geog-
raphy (Miller and Bridwell, 2009) is based upon concepts from
physics. Lefebvre (2004)'s approach for rhythm analysis could
also be used as a new operational approach within the spatial
event tradition; his 'alignments' of urban rhythms - arrhythmia,
polyrhythmia, eurhythmia, and isorhythmia - were all borrowed
from medical literature describing rhythms in the human body.
DNA sequence alignment techniques have also been adapted
to analyze daily urban events in space and time (Shoval and
Isaacson, 2007).
If all these four traditions of urban modeling are so permeable,
it is natural to ask whether they will continue to diverge or to
converge some unified theory of cities? It seems to me that
complexity, or polyplexity as Couclelis (2009) called it, is a
concept that could serve as a general umbrella that can tie all four
traditions together. It is beyond the scope of this chapter to discuss
this unified framework for linking the four traditions, but basic
ground work has already been laid out by Batty (2004), Wilson
(2000), and Allen, Strathern, and Baldwin (2007). Technological
convergence to the new web-based digital environment, coupled
with continued efforts to address global critical issues, could
also facilitate further synthetic development of urban modeling.
Otherwise, urban modeling could suffer the same fate as regional
science (Barnes, 2004).
Summary and concluding
remarks
We have an incapacity for proving anything which no amount
of dogmatism can overcome; we have an idea of truth which
no amount of skepticism can overcome
B. Pascal
Using Stephen Pepper's world hypotheses as a guiding frame-
work, this chapter painted a broad-brush picture of urban
analysis and modeling during the past 50 years. As revealed
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