What is SELES? (expanded)

The following is a structured but short introduction to SELES with links to definitions in Wikipedia and to SELES.info Documentation pages.

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.

Is SELES a model?
No! There are hundreds of models that have been built with SELES so it is inaccurate to speak of SELES as a model. SELES is actually two tools: (1) a high-level, declarative modelling language, used to specify each of the processes and agents acting in a model, and (2) a discrete-event simulation engine that interprets and executes the model. Read here about the SELES Paradigm.

Is SELES a black box?
No. The specification of each scenario and its attendent sub-models in ordinary ascii text files serves to provide a transparent window into each model. The result is that models may be easily compared, modified, and reused. Anyone can learn to interpret SELES model files. Hardy souls with a programming background (or others with sufficent tenacity) can be writing SELES code after a few weeks of study. This website is full of documentation and examples. Tutorials and courses are offered.

Is SELES flexible?
Yes, the SELES language is flexibile; 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.

What types of models can I build with SELES?
SELES has been used to build and run models that have combined aspects of cellular automata, discrete event simulation, spatio-temporal Markov models, and individual-based models.

What do you mean by Spatio-Temporal?
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.

Does SELES use cells, cohorts, patches, what?
The basic spatial unit in SELES is a cell, contrasting with patch-based approaches such as described in Wu and Levin (1997) or as geographic strata/landuse footprints as used in the ALCES model. However, SELES models can be constructed to permit multi-cell patches to behave as a unit. The layers input into SELES must be of the same scale. By this we mean they must have identical cell resolution (e.g. 1 ha or 100 ha) and extent (rows and columns of cells). Model spatial dimensions are determined by the user and will depend upon the quality of the data used to generate the input layers, the amount of memory in your computer, and the amount of time you have to run the model.

What raster file types are supported?
SELES can read, display and write the following raster file types: GRASS, GRASS COMPRESSED, GRASS ASCII, ARC ASCII, ERDAS8, and ERDAS16. Although SELES has some tools for aligning layers and scaling data, most users prepare their data using GIS software such as Manifold or ArcView.

What is a behaviour definition?
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. Behavours are captured via the following properties: Initial State, Return Time, Event Location, Number of Clusters, Probability of Initiation, Transitions, Spread Time, Spread Location, Number of Spread Recipients, Probability of Spread, EndCluster, and EndEvent. Descriptions of these properties can be found in Model_Builder%27s_Guide_Chapter_7

What are scenarios?
The set of initial conditions (raster layers), coupled with a set of landscape events and agents, is called a scenario. This hierarchy 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.