# The MESSAGE*ix* framework¶

## Overview and scope¶

MESSAGE*ix* is a versatile, open-source, dynamic systems-optimization modelling framework.
It was developed for strategic energy planning and integrated assessment of energy-engineering-economy-environment systems (E4).
The framework can be applied to analyse scenarios of the energy system transformation under technical-engineering constraints and political-societal considerations.
The optimization model can be linked to the general-economy MACRO model to incorporate feedback between prices and demand levels for energy and commodities.
The equations are implemented in the mathematical programming system GAMS for numerical solution of a model instance.

The MESSAGE*ix* framework is fully integrated with IIASA’s *ix modeling platform* (ixmp), a data warehouse for high-powered numerical scenario analysis.
The platform supports an efficient workflow between original input data sources, the implementation of the mathematical model formulation, and the analysis of numerical results.
The platform can be accessed via a web-based user interface and application programming interfaces (API) to the scientific programming languages Python and R.
The platform also includes a generic data exchange API to GAMS for numerical computation.

This documentation provides an introduction and the mathematical formulation of the MESSAGE*ix* equations and auxiliary functions.
For the scientific reference of the framework, see Huppmann et al. (2019) [1].
The formulation of MESSAGE*ix* is a re-implementation and extension of ‘MESSAGE V’ (Messner and Strubegger, 1995 [5]), the Integrated Assessment model developed at the International Institute for Applied Systems Analysis (IIASA) since the 1980s.
For an overview of the MESSAGE*ix* model used at the IIASA Energy Program and a list of recent publications, please refer to the MESSAGE-GLOBIOM documentation website.

## Getting Started¶

Have a question? First, check the Frequently asked questions, then try the community Google group:

- on the Web at https://groups.google.com/d/forum/message_ix, or
- via e-mail at <message_ix@googlegroups.com>.

## Detailed documentation¶

- MESSAGE
*ix*framework overview - Python & R API
- Mathematical specification
- Sets and mappings definition
- Parameter definition
- General parameters of the MESSAGE
*ix*implementation - Parameters of the Resources section
- Parameters of the Demand section
- Parameters of the Technology section
- Parameters of the Emission section
- Parameters of the Land-Use model emulator section
- Parameters of the Share Constraints section
- Parameters of the Relations section
- Fixed variable values

- General parameters of the MESSAGE
- Mathematical formulation (core model)
- Notation declaration
- Objective function
- Regional system cost accounting function
- Resource and commodity section
- Technology section
- System reliability and flexibility requirements
- Constraints on shares of technologies and commodities
- Emission section
- Land-use model emulator section
- Section of generic relations (linear constraints)

- Solve statement workflow
- Standard output reports
- Auxiliary investment parameters
- MACRO - Mathematical formulation

- Developing MESSAGE
*ix*models

## Using and contributing to MESSAGE*ix*¶

MESSAGE*ix* and the *ix modeling platform* are licensed under the APACHE 2.0 open-source license.

Anyone is encouraged to use the framework to develop energy system and integrated assessment models! Please see the User guidelines and notice for using the framework in scientific research. Contributions to the framework itself, which enable new features across all models, are also welcome.