Table 8‑3 Comparison of open source simulation/modelling toolkits

Table 8‑4 summarises information for three selected shareware/freeware toolkits, StarLogo, NetLogo and OBEUS:

StarLogo: is a modelling system developed at the Media Laboratory, Massachusetts Institute of Technology (MIT). Unlike the other six agent-based s/m systems discussed in this section, both StarLogo and NetLogo models are programmed procedurally, as opposed to having an object-oriented structure. Thus, models developed with StarLogo do not benefit from the similarity in abstraction shared between the agent-based and object-oriented paradigms. Furthermore, StarLogo lacks the same flexibility offered by open source systems, since modellers are constrained to the functionality provided by the system. However, the StarLogo website indicates that an open source version of the system (OpenStarLogo) has been developed and will be available in the near future. Despite these limitations, StarLogo is very easy to use, notably for people with very little programming experience. Dynamic charting of model output during a simulation is provided. In addition, a number of demonstration models and detailed ‘how-to’ documentation relating to these models is supplied with StarLogo, and many more are available to download from the World Wide Web. Batty et al. (1998) have used StarLogo to examine visitor movement within London’s Tate Gallery, examining how changes in room configuration can affect visitor movement between exhibits.

NetLogo: originally named StarLogoT, is a variant of StarLogo, originally developed at the Centre for Connected Learning and Computer-Based Modelling at Northwestern University. The critical distinction between the two s/m systems is that NetLogo is specifically designed for the deployment of models over the Internet. Both NetLogo and StarLogo provide functionality to import image files, which can be used to define the environments within which agents are located, thus facilitating the development of spatial models. NetLogo has been used to develop applications in disciplines varying from biology and physics to the social sciences. Extensive ‘how-to’ documentation, tutorials and demonstration models are available from the system website, and functionality can be extended through Application Programming Interfaces (APIs), although the source code for the system is currently unavailable.

OBEUS: Object-Based Environment for Urban Simulation, was developed at Tel Aviv University, Israel. Based on the theory of Geographic Automata Systems (GAS; Benenson and Torrens, 2004), it is designed for the simulation of urban phenomena; specifically in a geospatial context. GAS considers an urban system as consisting of objects that are either fixed (e.g. houses or roads) or non-fixed (e.g. people or cars). OBEUS is implemented in the Microsoft.NET framework, but relies on several third-party components (Microsoft.NET Framework, Borland C# compiler, etc.), which must be installed in order to operate the system. OBEUS provides a GUI to develop the structure of a model, although the behaviour and interaction rules of agents must be programmed using one of the Microsoft.NET languages (e.g. C#, C++, or Visual Basic, etc.). Consequently, moderate to strong programming skills are required. OBEUS has been used to develop a number of spatially explicit models, including the simulation of ethnic residential distributions within the Yaffo area of Tel Aviv between 1955 and 1995 (Benenson et al., 2002, Benenson et al., 2005), and street parking and urban sprawl (Benenson et al., 2004).

Table 8‑4 Comparison of shareware/freeware simulation/modelling systems

Table 8‑5 Comparison of proprietary simulation/modelling systems

Table 8‑5 summarises information for two proprietary toolkits, AgentSheets and AnyLogic, each of which is described in more detail below. As with many other commercial software products, both have much functionality and ongoing development that cannot be adequately described here, and readers are recommended to visit the web sites for the products to obtain more details and examples.

AgentSheets is a proprietary s/m system that allows modellers with limited programming experience to develop an agent-based model, because models are developed through a GUI (Repenning et al., 2000). A number of demonstration models are available from the system website. For example, Sustainopolis is a simulation analogous to the computer game SimCity that allows investigation of pollution dispersal within a city. Carvalho (2000) has used AgentSheets extensively to teach undergraduate students. He comments that it is easy to use the system to develop models quickly and provides students with hands-on experience of ABM without the need to learn a programming language. However, he also found that models created with AgentSheets were limited in their sophistication (notably in terms of the complexity of representation of agent behaviour and interaction). Furthermore, agents are limited to movement within a two-dimensional cell-based environment.

AnyLogic is a more sophisticated offering that incorporates a range of functionality for the development of agent-based models. For example, models can dynamically read and write data to spreadsheets or databases during a simulation run, as well as dynamically chart model output. Furthermore, external programs can be initiated from within an AnyLogic model for dynamic communication of information, and vice versa. However, AnyLogic models can only be created on Microsoft operating systems, although a simulation can be run on any Java-enabled operating system once compiled (e.g. a Macintosh operating system). The AnyLogic website notes that models have been developed for a diverse range of applications including: the study of social, urban and ecosystem dynamics (e.g. a predator-prey system); planning of healthcare schemes (e.g. the impact of safe syringe usage on HIV diffusion); computer and telecommunication networks (e.g. the placement of cellular phone base stations); and the location of emergency services and call centres. However, the source code of these examples and/or documentation of these models is not unavailable.

The example illustrated in Figure 8‑5 seeks to predict transport load and housing allocation (up to March 2009) within a city comprised of 5 independent zones. Each zone contains housing and business units, with various qualities of habitation and roads. Households may contain multiple members, who may work at various enterprises. Households can move in and out of the city, merge or separate, and even relocate to different zones (with an impact on travel patterns). Household members can change jobs when current ones become unsatisfactory (e.g. because of high living costs or low pay). Households whose prosperity improves may seek a better location to live within the city, which in turn may require them to purchase cars, resulting in raised CO₂ emissions.

Figure 8‑5 An urban and transport dynamics model developed in AnyLogic (2006)

Source: http://www.xjtek.com/anylogic/demo_models/social_dynamics/