Model Builder's Guide

Model Builder’s Guide

Documentation Version SELES v3.1

The Spatially Explicit Landscape Event Simulator (SELES) is a tool that provides a structured framework to guide the development and facilitate the rapid prototyping of spatial landscape models. The heart of SELES is a high-level, declarative modelling language, used to specify each of the processes and agents acting in a model, and a discrete-event simulation engine that interprets and executes the model. The specification of the model serves as a fairly clear description of the model semantics, and thus models may be easily compared, modified, and reused. The SELES language is general enough to allow the construction of models that are quasi-continuous, periodic, or episodic; with a fixed or variable time step; that are deterministic, process-oriented, or stochastic; and in which processes may operate locally, regionally, or globally and be either spreading or non-spreading. SELES models can combine aspects of cellular automata (Itami, 1994), discrete-event simulation (de Vasconcelos and Zeigler, 1993), spatio-temporal Markov models (Baltzer et al., 1998), and individual-based models.

All SELES models are composed of a set of raster layers, which represent the initial state, along with a definition of behaviour, which is used to simulate changes over time to the initial state. The basic spatial unit is a cell, contrasting with patch-based approaches such as described in (Wu and Levin 1997), although SELES models could be constructed to permit multi-cell patches to behave as a unit. The behaviour of a SELES model is described with a set of quasi-independent processes or agents of change. Each such agent is called a landscape event or a landscape agent, which we describe in detail in later sections. The initial conditions, coupled with the set of landscape events and agents, is called a scenario. This terminology allows us to differentiate between the overall simulation model and the individual spatial raster models, static landscape models and landscape event models that make up the scenario.

This document describes how to construct and run models using SELES. It is the primary reference document for SELES modellers and gives links to other documentation available. It contains specifications, instructions, hints and cautions of how to construct spatio-temporal simulation models with the SELES modelling system, in particular the conceptual basis for SELES landscape events and landscape agents. Understanding these is critical to apply SELES to transform a formal problem statement and conceptual model to a SELES simulation model.

The next section gives an overview of the SELES modelling paradigm. Section 2 covers input data formats. Section 3 covers static model generators, and statistical summary models. Section 4 covers dynamic model configuration. Section 5 covers general issues related to landscape events and agents, while section 6 and 7 cover details of events and agents. Section 8 describes the SELES language for building events and agents, and for some static models. The following are the other SELES documents referred to in this guide: SELES Scenario Reference: A description of SELES scenario scripting files. SELES/NT User Guide: A user’s guide for the SELES NT modelling environment/user interface software that describes how to load and execute SELES models.

Table of Contents

1 Building Spatio-temporal Models with SELES

2 Input Data

3 Static models

4 Dynamic model configuration

5 SELES Landscape Events and Landscape Agents

6 Landscape Events

7 SELES Landscape Agents

8 Expression Language: Specifying Landscape Events and Cell Expressions

9 References