WIP

docs/src/getting-started.md

@@ -144,3 +144,35 @@ Note: This should be a separate page... to do, WIP
 explain FT
 explain AbstractModel and why, etc.
 
+Existing Earth System Models and Land Surface Models are monolythique and the scientific community
+has asked for modularity in those models for a long time, as currently making modifications in 
+existing models is a task requiring a lot of time and money. 
+
+ClimaLand takes advantage of Julia multiple dispatch to build a modular model. 
+
+You can find detailed explanation on Julia multiple dispatch here, but I will give a brief overview
+and explain how we use it to build a modular land model in ClimaLand. 
+
+The core idea is that functions can have multiple methods depending on their arguments number or type. 
+
+For example, leaf transpiration is a function of stomatal conductance. Many models exists for stomatal conductance, 
+such as the Medlyn optimality model or the Ball-Berry model.
+
+We are going to create a new type, that we call "Abstract" type because it is not a fundamental type
+(Number, Real, Float, Integer...), but a subtype. For example: 
+
+```jl
+abstract type AbstractStomatalConductanceModel{FT} <: AbstractModel{FT} end
+abstract type MedlynConductanceModel <: AbstractStomatalConductanceModel{FT} end
+abstract type BallBerryConductanceModel <: AbstractStomatalConductanceModel{FT} end
+```
+
+now, when we call the function `function leaf_transpiration(conductance::AbstractStomatalConductanceModel)`, 
+conductance can be either Medlyn of BallBerry. 
+
+ClimaLand does this at multiple level, for example, our AbstractCanopyModel is made of photosynthesis, conductance, hydraulics, etc. 
+Similarly to AbstractConductanceModel, the AbstractCanopyModel can have multiple configurations that the rest of the model can dispatch 
+on, without changing anything. 
+
+This approach allow us to build ClimaLand as a puzzle, where we assemble pieces of many sizes, and can swap them easily. 
+