diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
index 0000000..e965a3d
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,4 @@
+# Changelog
+
+ProcessBasedModelling.jl follows semver 2.0.
+Changelog is kept with respect to v1 release.
\ No newline at end of file
diff --git a/docs/Project.toml b/docs/Project.toml
index ed92fe2..077d0f9 100644
--- a/docs/Project.toml
+++ b/docs/Project.toml
@@ -5,4 +5,3 @@ DocumenterCitations = "daee34ce-89f3-4625-b898-19384cb65244"
 DocumenterTools = "35a29f4d-8980-5a13-9543-d66fff28ecb8"
 DynamicalSystems = "61744808-ddfa-5f27-97ff-6e42cc95d634"
 ModelingToolkit = "961ee093-0014-501f-94e3-6117800e7a78"
-OrdinaryDiffEq = "1dea7af3-3e70-54e6-95c3-0bf5283fa5ed"
diff --git a/docs/src/index.md b/docs/src/index.md
index 3e5c6e9..adcbba5 100644
--- a/docs/src/index.md
+++ b/docs/src/index.md
@@ -33,7 +33,6 @@ symbolically using ModelingToolkit.jl (**MTK**). We define
 
 ```@example MAIN
 using ModelingToolkit
-using OrdinaryDiffEq: Tsit5
 
 @variables t # independent variable _without_ units
 @variables z(t) = 0.0
@@ -78,9 +77,10 @@ The error message is unhelpful as all variables are reported as "potentially mis
 At least on the basis of our scientific reasoning however, both ``x, z`` have an equation.
 It is ``y`` that ``x`` introduced that does not have an equation.
 Moreover, in our experience these error messages become increasingly less useful when a model has many equations and/or variables, as many variables get cited as "missing" from the variable map even when only one should be.
+This makes it difficult to quickly find out where the "mistake" happened in the equations.
 
-**PBM** resolves these problems and always gives accurate error messages when it comes to
-the construction of the system of equations.
+**PBM** resolves these problems and always gives accurate error messages when
+it comes to the construction of the system of equations.
 This is because on top of the variable map that MTK constructs automatically, **PBM** requires the user to implicitly provide a map of variables to processes that govern said variables. **PBM** creates the map automatically, the only thing the user has to do is to define the equations in terms of what [`processes_to_mtkmodel`](@ref) wants (which are either [`Process`](@ref)es or `Equation`s as above).
 
 Here is what the user defines to make the same system of equations via **PBM**:
@@ -199,12 +199,17 @@ ProcessBasedModelling.NoTimeDerivative
 ProcessBasedModelling.lhs
 ```
 
-## Utility functions
+## Automatic named parameters
 
 ```@docs
-default_value
-has_variable
 new_derived_named_parameter
 @convert_to_parameters
 LiteralParameter
 ```
+
+## Utility functions
+
+```@docs
+default_value
+has_symbolic_var
+```
diff --git a/src/ProcessBasedModelling.jl b/src/ProcessBasedModelling.jl
index 0c233d5..be92da7 100644
--- a/src/ProcessBasedModelling.jl
+++ b/src/ProcessBasedModelling.jl
@@ -25,8 +25,9 @@ export t
 export Process, ParameterProcess, TimeDerivative, ExpRelaxation, AdditionProcess
 export processes_to_mtkmodel
 export new_derived_named_parameter
-export has_variable, default_value
+export has_symbolic_var, default_value
 export @convert_to_parameters, LiteralParameter
-export lhs_variable, rhs, lhs
+# export lhs_variable, rhs, lhs # I am not sure whether these should be exported.
+export all_equations
 
 end
diff --git a/src/make.jl b/src/make.jl
index c568494..136545a 100644
--- a/src/make.jl
+++ b/src/make.jl
@@ -33,8 +33,8 @@ function processes_to_mtkmodel(_processes, _default = [];
     processes = expand_multi_processes(_processes)
     default = default_dict(_default)
     # Setup: obtain lhs-variables so we can track new variables that are not
-    # in this vector
-    lhs_vars = map(lhs_variable, processes)
+    # in this vector. The vector has to be of type `Num`
+    lhs_vars = Num[lhs_variable(p) for p in processes]
     ensure_unique_vars(lhs_vars)
     # First pass: generate equations from given processes
     # and collect variables without equations
diff --git a/src/processes_basic.jl b/src/processes_basic.jl
index fb4b195..80541e4 100644
--- a/src/processes_basic.jl
+++ b/src/processes_basic.jl
@@ -17,7 +17,7 @@ struct ParameterProcess <: Process
     variable
     value
     function ParameterProcess(variable, value)
-        var = new_derived_named_parameter(variable, value, "0")
+        var = new_derived_named_parameter(variable, value, "0"; prefix = false)
         return new(variable, var)
     end
 end
diff --git a/src/utils.jl b/src/utils.jl
index 43f2e92..6bffc53 100644
--- a/src/utils.jl
+++ b/src/utils.jl
@@ -14,22 +14,48 @@ _literalvalue(x) = x
 _literalvalue(p::LiteralParameter) = p.p
 
 """
-    has_variable(eq, var)
+    has_symbolic_var(eqs, var)
 
-Return `true` if variable `var` exists in the equation(s) `eq`, `false` otherwise.
-Function works irrespectively if `var` is an `@variable` or `@parameter`.
+Return `true` if symbolic variable `var` exists in the equation(s) `eq`, `false` otherwise.
+This works for either `@parameters` or `@variables`.
+If `var` is a `Symbol` isntead of a `Num`, all variables are converted to their names
+and equality is checked on the basis of the name only.
+
+    has_symbolic_var(model, var)
+
+When given a MTK model (such as `ODESystem`) search in _all_ the equations of the system,
+including observed variables.
 """
-function has_variable(eq::Equation, var)
+function has_symbolic_var(eq::Equation, var)
     vars = get_variables(eq)
+    return _has_thing(var, vars)
+end
+has_symbolic_var(eqs::Vector{Equation}, var) = any(eq -> has_symbolic_var(eq, var), eqs)
+has_symbolic_var(mtk, var) = has_symbolic_var(all_equations(mtk), var)
+
+function _has_thing(var::Num, vars)
     return any(isequal(var), vars)
 end
-has_variable(eqs, var) = any(eq -> has_variable(eq, var), eqs)
+function _has_thing(var::Symbol, vars)
+    vars = ModelingToolkit.getname.(vars)
+    var = ModelingToolkit.getname(var)
+    return any(isequal(var), vars)
+end
+
+"""
+    all_equations(model)
+
+Equivalent with `vcat(equations(model), observed(model))`.
+"""
+all_equations(model) = vcat(equations(model), observed(model))
 
 """
     default_value(x)
 
 Return the default value of a symbolic variable `x` or `nothing`
 if it doesn't have any. Return `x` if `x` is not a symbolic variable.
+The difference with `ModelingToolkit.getdefault` is that this function will
+not error on the absence of a default value.
 """
 default_value(x) = x
 default_value(x::Num) = default_value(x.val)
@@ -64,11 +90,14 @@ end
 
 If `value isa Num` return `value`.
 If `value isa LiteralParameter`, replace it with its literal value.
-Otherwise, create a new MTK `@parameter`
-whose name is created from `variable` (which could also be just a `Symbol`) by adding the `extra` string.
-If the keyword `prefix == false` the `extra` is added at the end after a `_`. Otherwise
-it is added at the start, then a `_` and then the variable name.
-The keyword `connector = "_"` is what connects the `extra` with the name.
+Otherwise, create a new MTK `@parameter` whose name is created from `variable`
+(which could also be just a `Symbol`) by adding the `extra` string.
+
+**Keywords**:
+
+- `prefix = true`: whether the `extra` is added at the start or the end, connecting
+  with the with the `connector`.
+- `connector = "_"`: what to use to connect `extra` with the name.
 
 
 For example,
@@ -83,10 +112,10 @@ new_derived_named_parameter(v, value::Num, extra::String; kw...) = value
 new_derived_named_parameter(v, value::LiteralParameter, extra::String; kw...) = value.p
 function new_derived_named_parameter(v, value::Real, extra; connector = "_", prefix = true)
     n = string(ModelingToolkit.getname(v))
-    newstring = if !(prefix)
-        n*connector*extra
-    else
+    newstring = if prefix
         extra*connector*n
+    else
+        n*connector*extra
     end
     new_derived_named_parameter(newstring, value)
 end
diff --git a/test/runtests.jl b/test/runtests.jl
index adcc5e8..8d9dd41 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -55,7 +55,7 @@ using OrdinaryDiffEq
 
     sys = structural_simplify(sys)
     @test length(unknowns(sys)) == 1
-    @test has_variable(equations(sys), T)
+    @test has_symbolic_var(equations(sys), T)
 
     u0s = [[300.0], [100.0]]
     ufs = []
@@ -81,7 +81,7 @@ using OrdinaryDiffEq
 
     sys = structural_simplify(sys)
     @test length(unknowns(sys)) == 1
-    @test has_variable(equations(sys), T)
+    @test has_symbolic_var(equations(sys), T)
 
 end
 
@@ -160,12 +160,9 @@ end
         @test p == 0.5
     end
 
-
-    @testset "new named var"
-
 end
 
-@testset "default processes" begin
+@testset "default processes, has_thing" begin
     @variables x(t) = 0.5
     @variables y(t) = 0.5
     @variables z(t) = 0.5
@@ -174,15 +171,19 @@ end
     processes = [
         TimeDerivative(x, x^2, 1.2),
         ParameterProcess(y),
-        ExpRelaxation(z, x^2),
+        ExpRelaxation(z, x^2, 0.5),
         AdditionProcess(ParameterProcess(w), x^2),
         AdditionProcess(TimeDerivative(q, x^2, 1.2), ExpRelaxation(q, x^2))
     ]
     mtk = processes_to_mtkmodel(processes)
-    eqs = equations(mtk)
-    @test has_variable(eqs, x)
-    @test has_variable(eqs, y)
-    @test has_variable(eqs, z)
-    @test has_variable(eqs, w)
-    @test has_variable(eqs, q)
+    mtk = structural_simplify(mtk)
+    eqs = all_equations(mtk)
+    @test has_symbolic_var(eqs, x)
+    @test has_symbolic_var(eqs, y)
+    @test has_symbolic_var(eqs, :z)
+    @test has_symbolic_var(eqs, mtk.w)
+    @test has_symbolic_var(eqs, q)
+    @test has_symbolic_var(mtk, q)
+    @test has_symbolic_var(eqs, mtk.τ_z)
+    @test has_symbolic_var(eqs, :w_0)
 end
\ No newline at end of file