Space is the Machine, with a Ghost Inside

The purpose of this paper is to report efforts towards the construction of a  model for urban spatial dynamics simulation, based on multi-agents and space.  The underlying idea is to have urban space producers and consumers operating  in a two-layer, two-circuit model. The first layer holds urban space and its  successive transformations, a second layer contains agents related to space, the  first circuit simulates space production, and a second one simulates space  consumption. Relationship between layers is represented as objective spatial  features that agents are submitted to (the machine) and subjective meanings  agents attach to each spatial feature (the ghost). While space works always in  the same way, meanings vary according to each agentis background and  context. Relationships between circuits are represented by means of a market  game in which producers try to maximize their profits by gambling with their  risks, whereas consumers try to foresee the spatial distribution of local  externalities that maximizes their utilities and investments. Urban Spatial  Features are captured through centrality and land use patterns, every single  agentis action leads to changes in both patterns. Producersi profit is a function  of built form location. Consumersi local externalities are concerned basically  with present and future services. The model iteration is twofold: first it  generates and allocates a number of built forms within a previously determined  spatial system (a cellular matrix, for example), and second it allocates users to  built forms. Population of users have its social profile and growth rate  externally determined. Built form allocation is decided on the basis of a  combination of profit Xrisk perspectives. Usersi locational choice is supported  by accessibility to services and present/future neighbourhood profile. Built  form allocation works as parameter for usersi locational assessment, whereas  users choices are used as parameters for developers. The model tends to  adjust itself, in terms of quantities and types of built forms to be erected,  although through a market lag of some iterations. Allocations are always made  through weighted draws, so that mutations (non deterministic allocations) do  occur.

Urban convergence: morphology and attraction

A model, based on detailed descriptions of spatial configuration and a probabilistic approach to the user's choice, is proposed to measure the relationship between demand and supply locations in urban local systems. According to this model, the articulation of the public space grid, associated to the uneven distribution of facilities, generates a powered supply network to which demand locations are related. Choice, as well as demand satisfaction, will then be a function of the relative position (centrality) and attractiveness of supply locations. The model gives a simultaneous account of the spatial opportunity of demand and the spatial convergence of supply. Concurrently it can offer a picture of the stability of space in terms of possible land-use changes.

Modelling intraurban configurational development

A set of models for intraurban context applications is proposed that enables: (a) the description of urban configurations, by the use of simple spatial categories and concepts of areal diferentiation; (b) the assessment of performance of urban configurations, by the application of centrality approaches that permit reliable correlations to behavioural aspects of urban spatial structure: depending on the comprehensiveness of the chosen models such an assessment could give a picture for the whole system or the performance of discrete components within the context of the system; (c) the potentiality and stability of configurational systems, from the point of view of change. The approach differs from mainstream urban systems studies in two ways: first an intraurban scale was defined to suit localized and detailed experimentation, as usually found in urban design situations; second, the focus was shifted from the activity system to the configurational system, again to suit urban design processes. The research summarized in this paper gives insights into the scaling of urban phenomena, suggesting that complexity, identified in large-scale urban systems, is also present in local ones, and that urban development occurs in simultaneous, although self-similar, scales.

A study of intra-urban configurational development in Porto Alegre - Brazil

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Built form and urban configuration development simulation

The “centrality/potential” model, proposed by Krafta (1994), for configurational development, aims at the simulation of inner city built form growth. This is generally achieved by simulating the uneven distribution of floor area increments, resulting from replacement of old buildings, considered “devalued capitali form new ones. The model considers two main variables - public urban space system and built form - and treats them unevenly, the former is extensively disaggregated whereas the latter is not. This feature enables the model to make just a rough account of intra-urban built form development. The issue of built form simulation is then taken further in the following way: a) Urban built form is disaggregated by types. Buildings are classified by a cross combination of scale, purpose, age and quality standard, b) The city is itself considered as a set of intertwined typologic cities. This means that each unit of public space is identified by its dominant built form type, producing a multilayered-discontinuous city. Each one has its own market characteristics: rentability, technological availability and demand size, c) The market constraints determine which layer-city has priority over the others, as well as each one's size of growth. References to rentability and demand size gives each built form type priorities for development d) Spatial conditions, in the form of particular evaluation of centrality and spatial opportunity measures, regulates the distribution of built form increments and typological succession. Locational values, denoted by centrality and spatial opportunity measures, area differently accounted for in each layer-city simulation. e) Simulation is obtained by “runningi the model recursively. Each built form type is simulated separately and in hyerarquical order, so that priority and replacement of built form types is acknowledged properly

Environment - Urban Interface within Urban Growth

This work presents the synthesis of a model of urban growth dedicated to  accomplish simulations of urban spatial dynamics, based on integrated urban  and environmental factors and promoting simultaneity among external and  internal growth. The city and surrounding environment are captured and  modeled in computational ambient, by application of the centrality / potential  model (Krafta, 1994 and 1999), with support of graph theory, cellular  automata, GIS and geocomputation. The model assumes the city as a field of  opportunities for obtaining income, mediated by the space, which is composed  of urban and environmental attributes, that work as attractors or as resistances  for the urban growth. The space configuration and the distribution of those  attributes generate tensions that differentiate qualitatively and quantitatively  the space, through the centrality measure (built with the support of graphs  techniques), coming to provoke growth in places with larger potential of  development (built with the help of techniques of CA - cellular automata).  Growths above environmental thresholds are considered problems, generated  and overcome in the same process of production of the urban space. Iterations  of that process offer a dynamic behaviour to the model, allowing to observe  the growth process along the time. The model presents several possibilities: a)  urban - natural environment integration, b) internal and external growth  integration, c) variety in the scale, d) GIS integration and geocomputation, e)  user interface, f) calibration, g) theoretical possibilities, and h) practical  possibilities. 

Urban Land Value Distribution UnderConfigurational Scrutiny

In the present study were evaluated land parceling problems under aspects of spatial configuration related to land value (lv). Paradoxical cases occur in urban spaces, such as low spatial differentiation and high lv, or vice-versa. Determined urban areas are identified as having high centrality, with intense land use and occupation, and, therefore, high market value. Conversely, other urban areas are identified as having low centrality value, certain degradation, or lack of infrastructure and urban equipment, and, consequently, low lv. Empirical studies have proved satisfactory results interms of the correlation between measures of configuration and lv. These studies verify the convenience of the models used to describe significant aspects of spatial differentiation. The complementation of the methodological proposal is identified, and other components of urban space are calculated (plot dimension, infrastructure, normative aspects, etc). These are determinant measures that characterize the local factor associated with measures that determine the morphological differentiation.This differentiation demonstrated that land value distribution, besides following centrality, depends, in greater or lesser extent, on the local factor. The results obtained, through a model that combines measures of centrality with local characteristics, approached reality because the model incorporated a greater number of variables which allowed the verification of correlated socioeconomic and spatial matters related to parceling, value, and configuration