Friday, September 28, 2007

Integrating Geographic Information Systems and ABM

We do not often publicise books on this blog but we felt we would make an exception with this book: "Integrating Geographic Information Systems and Agent-Based Modeling Techniques for Simulating Social and Ecological Processes" edited by Randy Gimblett. According to Google Scholar it is cited 78 times in a diverse range of articles.

For those interested in integrating GIS and ABM, this book provides one of the first detailed accounts of such integration and its applications. Including articles by Westervelt on the coupling of GIS and ABM and various articles by Gimblett and others which highlight how GIS can be combined with ABM thus allowing one to relate models directly to place.

Other books which we have found valuable in our research can be found in our reading list.

Thursday, September 27, 2007

Geospatial Simulation with Repast

After the previous post "ABM–S4–ESHIA Summer School" I thought it would be useful to draw peoples attention to a new CASA working paper entitled "The Repast Simulation / Modelling System for Geospatial Simulation." Which was the basis of talk two from the workshop Mike and I gave.

The abstract to the paper is: 'The use of simulation/modelling systems can simplify the implementation of agent-based models. Repast is one of the few simulation/modelling software systems that supports the integration of geospatial data especially that of vector-based geometries. This paper provides details about Repast specifically an overview, including its different development languages available to develop agent-based models. Before describing Repast’s core functionality and how models can be developed within it, specific emphasis will be placed on its ability to represent dynamics and incorporate geographical information. Once these elements of the system have been covered, a diverse list of Agent-Based Modelling (ABM) applications using Repast will be presented with particular emphasis on spatial applications utilizing Repast, in particular, those that utilize geospatial data.'

If you feel like you might be interested in this paper. It can be downloaded from here. As always any thoughts and comments are most welcome.

Full Reference:
Crooks, A. T. (2007), The Repast Simulation/Modelling System for Geospatial Simulation, Centre for Advanced Spatial Analysis (University College London): Working Paper 123, London, England. (pdf)



Geocomputational methods and modelling

Just a note to say Christian and myself have just contributed to a chapter in de Smith, M.J., Goodchild, M.F. and Longley, P.A. (2007) Geospatial Analysis: A Comprehensive Guide to Principles, Techniques and Software Tools (2nd Edition). The book will be out shortly but if you are interested in the chapter or the book in genral, a web version can be found Geospatial Analysis Web site.

The book explains in detail the principles and techniques of geospatial ananyis which are extremly useful when developing geographically explicit agent-based models along with GIS in general

The full reference for the chapter is:

Castle, C.J.E., Crooks, A.T., de Smith, M.J., Goodchild, M.F., and Longley, P.A., (2007), Geocomputational Methods and Modelling, in de Smith, M.J., Goodchild, M.F. and Longley, P.A. (eds.), Geospatial Analysis: A Comprehensive Guide to Principles, Techniques and Software Tools (2nd Edition), The Winchelsea Press, Winchelsea, UK.

Links: Geospatial Analysis Web site

Tuesday, September 25, 2007

ABM–S4–ESHIA Summer School

Mike Batty and myself have recently attended a summer school entitled 'Agent Based Models for Spatial Systems in Social Sciences Economic Science with Heterogeneous Interacting' or ABM–S4–ESHIA for short. This summer school was organized by both by the European GDR S4 (Spatial Simulation for the Social Sciences), and the ESHIA (Society for Economic Science with Heterogeneous Interacting Agents ). Full details about the talks including .pdfs can be found here.

While at the summer school Mike and myself gave a workshop entitled 'How to Build an Agent-Based Model'. I thought it would be useful to share this workshop/.pdfs to a wider audience. The workshop was organised into three parts/talks.

The first talk was given by Mike focusing on "Models and Theories: Science, Validation,
Verification and Calibration." Within this talk Mike discussed what should be considered when building an agent-based model. Specifically outlining what are models, types of models and how models can be based on 'Stylized Facts'. Before focusing on how to develop models using a software environment.

This lead to second talk presented by myself on how a geospatial agent-based model can be developed using such a software environment. In this case using Repast. Within this talk, there was a discussion of what Repast is, examples of models created in Repast specifically those utilising Raster and Vector data sets and what the difference between the two are.


The third talk was given by Mike which focused on Cellular Automata (CA). Within this talk there was a discussion on CA applications, specifically focusing on urban growth and land cover (LUCC) etc. This was followed by how one represents space and dynamics within models, the key elements of CA models and a list of groups actively researching urban phenomena utilizing CA models. To give an example of a CA model the DUEM model (Dynamic Urban Evolutionary Model) was given.

Hopefully in the future we will have time to develop this material in the future but for now you can download any of the talks as .pdf by clicking on the number one, two and three.


Tuesday, September 11, 2007

New Working Paper

Following on from a previous post we just penned a new working paper outlining in more detail the challenges modellers face when creating agent-based models focusing on geo-spatial phenomena. Note how the challenges have gone from five to seven. The paper is called “Key Challenges in Agent-Based Modelling for Geo-Spatial Simulation.” Below is the abstract:
Agent-based modelling (ABM) is fast becoming the dominant paradigm in social simulation due primarily to a worldview that suggests that complex systems emerge from the bottom-up, are highly decentralised, and are composed of a multitude of heterogeneous objects called agents. These agents act with some purpose and their interaction, usually through time and space, generates emergent order, often at higher levels than those at which such agents operate. ABM however raises as many challenges as it seeks to resolve. It is the purpose of this paper to catalogue these challenges and to illustrate them using three somewhat different agent-based models applied to city systems. The seven challenges we pose involve: the purpose for which the model is built, the extent to which the model is rooted in independent theory, the extent to which the model can be replicated, the ways the model might be verified, calibrated and validated, the way model dynamics are represented in terms of agent interactions, the extent to which the model is operational, and the way the model can be communicated and shared with others. Once catalogued, we then illustrate these challenges with a pedestrian model for emergency evacuation in central London, a hypothetical model of residential segregation tuned to London data which elaborates the standard Schelling (1971) model, and an agent-based residential location built according to spatial interactions principles, calibrated to trip data for Greater London. The ambiguities posed by this new style of modelling are drawn out as conclusions.

If you are still interested, click here to download the full paper, any comments or suggestions are most welcome.

Monday, September 10, 2007

Ascape

While being around for quite some time, the Ascape agent-based modelling framework is now available under an Open Source license. For some background on Ascape see the paper by Miles Parker in the JASSS which also highlights applications that have utilised Ascape to create agent-based models. The original Ascape page from the Brookings Institute might also be of interest along with the new page at http://ascape.sourceforge.net/


References/Links


Geocomputation 2007: Challenges in Agent-Based Modelling

Last week we attended the Geocomputation 2007 conference at the National Centre for Geocomputation at the National University of Ireland in Maynooth. We thought we would share the talk and the short paper entitled “Key Challenges in Agent-Based Modelling for Geo-Spatial Simulation.” This paper outlines some of the key challenges for ABM specifically relating it to geo-spatial simulation and how we at CASA are attempting to address these issues.


Any thoughts or comments would be more than welcome.
Click here to download the paper and here for the presentation.

Full Reference:
Crooks, A. T., Castle, C. J. E., and Batty, M. (2007), Key Challenges in Agent-Based Modelling for Geo-spatial Simulation, in Demšar, U (ed.), Proceedings of the 9th International Conference on Geocomputation, National Centre for Geocomputation, National University of Ireland, Maynooth, Ireland. (pdf)