SPARK: A Framework for Multi-Scale Agent-Based Biomedical Modeling

Background

Computational models in systems biology are intended to describe biological phenomena at various scales (Kitano, 2002). However, the ability to transcend multiple scales of biological phenomenon within a single, cohesive computational model remains a significant challenge to the biomedical modeling community. This capacity is particularly important for the goal of translating underlying mechanistic knowledge to the level of clinical relevance. Recently, translational systems biology has been introduced as a means of utilizing dynamic mathematical models and engineering principles to aid in the optimization of clinical practice (Vodovotz, 2008; An, 2008).

Traditional mathematical models in systems biology are built using statistics or differential equations. These models are best suited for circumstances in which the dimensions of the modeled biological problems are few. However, for most biological systems with a high degree of complexity, the models themselves quickly become intractable in terms of both analysis and computation. Agent-based modeling is an alternative technique with which to model complex biological systems. This type of modeling incorporates an object-oriented, rule-based, discrete event method of model construction (An, 2001; An, 2009; Bankes, 2002; Bonabeau, 2002; Grimm, 2005).

Earlier implementations of ABM-building software were geared towards developing models in the social sciences, such as Ascape (Inchiosa, 2002) and Repast (North, 2006), or towards general-purpose discrete-event simulations, such as MASON (Luke, 2003) and NetLogo (Wilensky, 1999). Among these, NetLogo is currently one of the most popular, particularly for nonformally-trained programmers, due to its user-friendly interface and the natural language-like syntax of its Logo-based programming language. These features greatly simplify the programming of ABMs for novice programmers. Many biomedical models have been developed successfully by using NetLogo (Mi, 2007; Li, 2008; An, 2004; Bailey, 2009). However, despite its utility, we believe that the construction of biomedical ABMs would benefit from some capabilities currently not found in NetLogo and similar software. These features include the ability to vary agent size, to employ continuous model space, to organize code into modules that can map to biological processes, as well as offering the potential for parallelization in distributed computer architectures.