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160 G. Polhill

as much to any other modelling approach as they do to agent-based models, noting
that models with a number of parameters commensurate with the available data may
be oversimplifying.
Unsatisfactory though some will find the idea that a model’s ontology might
be seen as subjective, the increased expressivity of agent-based models’ ontologies
over those of other formal modelling approaches places greater onus on the
assessment of these ontologies as part of the validation process. Methodologies for
assessing ontologies are still not at a sufficiently mature stage that there is a clear
‘standard’. We have argued that best practice would involve a separate knowledge
elicitation exercise with experts not involved in design and a comparison of the
resulting ontology (or an ontology generated from a similar process in by other
authors) with that of the model. Given interest in ontologies in other disciplines,
there is an opportunity for the agent-based modelling community to contribute to
this area, ensuring that tools and techniques can be tailored to meet any specific
requirements.

Acknowledgements We acknowledge funding from the Engineering and Physical Sciences
Research Council (award no. 91310127), the European Commission Framework Programme 7
‘GLAMURS’ project (grant agreement no. 613420) and the Scottish Government Rural Affairs,
Food and the Environment Strategic Research Programme, Theme 2: Productive and Sustainable
Land Management and Rural Economies. We are also grateful to Bruce Edmonds and Mark Brewer
for useful comments on earlier drafts of this chapter; any mistakes are of course our own.

Further Reading

Shalizi’s (2006) book chapter covers approaches to modelling (and measuring)
complex systems in a more formal and comprehensive way, with a focus on more
traditional mathematical modelling techniques. However, he also covers issues with
validation and penalization of parameters, including discussions of VC theory and
Ockham’s razor.
Sowa’s (1999) book on knowledge representation is a good introduction to vari-
ous issues in the field and covers various formalisms and underlying philosophical
questions that the formal representation of knowledge yields. Baader et al.’s (2003)
Description Logic Handbook goes in to more details on description logics. Another
book, which goes into some depth on controversies in the formal representation
of what otherwise seems to be a simple everyday concept, ‘if-then’, is Evans and
Over’s (2004) book, and this too is highly recommended.
Since one of the ways of validating ontologies is through engaging with
stakeholders, the Companion Modelling school of agent-based modelling, pioneered
especially by research teams based in France, is well worth familiarizing yourself
1
with. They have a website and a book (Etienne 2014) as well as several publications

1 https://www.commod.org/en <Accessed May 2017>.