The most significant part of MOI is the definition of the model API that is used to specify an instance of an optimization problem (e.g., by adding variables and constraints). Objects that implement the model API should inherit from the ModelLike 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 and provides methods to solve the model and interact with solutions. See the Solutions section for more details.


Throughout the rest of the manual, model is used as a generic ModelLike, and optimizer is used as a generic AbstractOptimizer.


MOI does not export functions, but for brevity we often omit qualifying names with the MOI module. Best practice is to have

using MathOptInterface
const MOI = MathOptInterface

and prefix all MOI methods with MOI. in user code. If a name is also available in base Julia, we always explicitly use the module prefix, for example, with MOI.get.


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), and properties of variables and constraints such as the name of a variable (VariableName).

There are four types of attributes:

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 and set functions.

Consult the docstsrings of each attribute for information on what it represents.

ModelLike API

The following attributes are available:

AbstractOptimizer API

The following attributes are available: