List model attributes in documentation

docs/src/manual/models.md

@@ -17,10 +17,9 @@ from the [`ModelLike`](@ref) abstract type.
 Notably missing from the model API is the method to solve an optimization
 problem. `ModelLike` objects may store an instance (e.g., in memory or backed by
 a file format) without being linked to a particular solver. In addition to the
-model API, MOI defines [`AbstractOptimizer`](@ref).
-
-*Optimizers* (or solvers) implement the model API (inheriting from `ModelLike`)
-and additionally provide methods to solve the model.
+model API, MOI defines [`AbstractOptimizer`](@ref) and provides methods to solve
+the model and interact with solutions. See the [Solutions](@ref manual_solutions)
+section for more details.
 
 !!! info
     Throughout the rest of the manual, `model` is used as a generic `ModelLike`,
@@ -39,14 +38,74 @@ and additionally provide methods to solve the model.
 
 ## Attributes
 
-Attributes can be set in different ways:
+Attributes are properties of the model that can be queried and modified. These
+include constants such as the number of variables in a model [`NumberOfVariables`](@ref)),
+and properties of variables and constraints such as the name of a variable
+([`VariableName`](@ref)).
+
+There are four types of attributes:
+
+ * Model attributes (subtypes of [`AbstractModelAttribute`](@ref)) refer to
+   properties of a model.
+ * Optimizer attributes (subtypes of [`AbstractOptimizerAttribute`](@ref)) refer
+   to properties of an optimizer.
+ * Constraint attributes (subtypes of [`AbstractConstraintAttribute`](@ref))
+   refer to properties of an individual constraint.
+ * Variable attributes (subtypes of [`AbstractVariableAttribute`](@ref)) refer
+   to properties of an individual variable.
+
+Some attributes are values that can be queried by the user but not modified,
+while other attributes can be modified by the user.
+
+All interactions with attributes occur through the [`get`](@ref) and [`set`](@ref)
+functions.
+
+Consult the docstsrings of each attribute for information on what it represents.
+
+## Model attributes
+
+The following attributes are available for models:
+
+ * [`Name`](@ref)
+ * [`ObjectiveFunction`](@ref)
+ * [`ObjectiveFunctionType`](@ref)
+ * [`ObjectiveSense`](@ref)
+ * [`NumberOfVariables`](@ref)
+ * [`ListOfVariableIndices`](@ref)
+ * [`ListOfConstraintTypesPresent`](@ref)
+ * [`NumberOfConstraints`](@ref)
+ * [`ListOfConstraintIndices`](@ref)
+ * [`ListOfOptimizerAttributesSet`](@ref)
+ * [`ListOfModelAttributesSet`](@ref)
+ * [`ListOfVariableAttributesSet`](@ref)
+ * [`ListOfConstraintAttributesSet`](@ref)
+
+## Optimizer attributes
+
+The following attributes are available for optimizers:
+
+ - [`SolverName`](@ref)
+ - [`RawOptimizerAttribute`](@ref)
+ - [`Silent`](@ref)
+ - [`TimeLimitSec`](@ref)
+ - [`NumberOfThreads`](@ref)
+ - [`RawSolver`](@ref)
 
-* it is either set when the model is created like [`SolverName`](@ref) and
-  [`RawSolver`](@ref),
-* or explicitly when the model is copied like [`ObjectiveSense`](@ref),
-* or implicitly, e.g., [`NumberOfVariables`](@ref) is implicitly set by
-  [`add_variable`](@ref) and [`ConstraintFunction`](@ref) is implicitly set by
-  [`add_constraint`](@ref).
-* or it is set to contain the result of the optimization during
-  [`optimize!`](@ref) like [`VariablePrimal`](@ref).
+In addition, optimizers should implement the following attributes to provide
+access to solutions:
 
+ - [`TerminationStatus`](@ref)
+ - [`TerminationStatusCode`](@ref)
+ - [`PrimalStatus`](@ref)
+ - [`DualStatus`](@ref)
+ - [`ResultStatusCode`](@ref)
+ - [`RawStatusString`](@ref)
+ - [`ResultCount`](@ref)
+ - [`ObjectiveValue`](@ref)
+ - [`DualObjectiveValue`](@ref)
+ - [`ObjectiveBound`](@ref)
+ - [`RelativeGap`](@ref)
+ - [`SolveTimeSec`](@ref)
+ - [`SimplexIterations`](@ref)
+ - [`BarrierIterations`](@ref)
+ - [`NodeCount`](@ref)

docs/src/manual/solutions.md

@@ -7,7 +7,7 @@ end
 DocTestFilters = [r"MathOptInterface|MOI"]
 ```
 
-# Solutions
+# [Solutions](@id manual_solutions)
 
 ## Solving and retrieving the results