update readme and docstrings

Author: hdavid16

README.md

@@ -107,6 +107,8 @@ Disjunctions can be nested by passing an additional `Disjunct` tag. The Logical
 
 Empty disjuncts are supported in GDP models. When used, the only constraints enforced on the model when the empty disjunct is selected are the global constraints and any other disjunction constraints defined.
 
+For convenience, the `Exactly(1)` selector constraint is added by default when adding a disjunction to the model. In other words, `@disjunction(model, Y)` will add the disjunction and automatically add the logical constraint `Y in Exactly(1)`. For nested disjunctions, the appropriate `Exactly` constraint is added (e.g., `@constraint(model, Y[1:2] in Exactly(Y[3]))`) to indicate that `Exactly 1` logical variable in `Y[1:2]` is set to `true` when `Y[3]` is `true`, and both variables in `Y[1:2]` are set to `false` when `Y[3]` is `false`, meaning the parent disjunct is not selected. Adding the `Exactly` selector constraint by default can be disabled by setting the keyword argument `exclusive` to `false` in the `@disjunction` macro.
+
 ## MIP Reformulations
 
 The following reformulation methods are currently supported:

src/macros.jl

@@ -155,8 +155,8 @@ The recognized keyword arguments in `kw_args` are the following:
     the constraint names are set to `base_name[...]` for each index `...` 
         of the axes `axes`.
 -  `container`: Specify the container type.
--  `exclusive`: Specify a `Bool` whether an constraint should be added to make 
-   the disjuncts strictly exlcusive of one another.
+-  `exclusive`: Specify a `Bool` whether a constraint should be added to 
+   only allow selecting one disjunct in the disjunction.
 
 To create disjunctions without macros, see [`disjunction`](@ref).
 """

src/reformulate.jl

@@ -49,10 +49,9 @@ end
 """
     requires_exclusive(method::AbstractReformulationMethod)
 
-Return a `Bool` whether `method` requires an the disjuncts to be exactly exclusive 
-for each disjunction (i.e., it requires an exactly one constraint). For new 
-reformulation method types, this should be extended to in case such a constraint 
-is required (defaults to `false` otherwise).
+Return a `Bool` whether `method` requires that `Exactly 1` disjunct be selected 
+as true for each disjunction. For new reformulation method types, this should be 
+extended to return `true` if such a constraint is required (defaults to `false` otherwise).
 """
 requires_exclusive(::AbstractReformulationMethod) = false