Active inference is a leading theory of perception, learning and decision
making, which can be applied to neuroscience, robotics, psychology, and machine
learning. Active inference is based on the expected free energy, which is
mostly justified by the intuitive plausibility of its formulations, e.g., the
risk plus ambiguity and information gain / pragmatic value formulations. This
paper seek to formalize the problem of deriving these formulations from a
single root expected free energy definition, i.e., the unification problem.
Then, we study two settings, each one having its own root expected free energy
definition. In the first setting, no justification for the expected free energy
has been proposed to date, but all the formulations can be recovered from it.
However, in this setting, the agent cannot have arbitrary prior preferences
over observations. Indeed, only a limited class of prior preferences over
observations is compatible with the likelihood mapping of the generative model.
In the second setting, a justification of the root expected free energy
definition is known, but this setting only accounts for two formulations, i.e.,
the risk over states plus ambiguity and entropy plus expected energy
formulations.

通过对单个根期望自由能定义的问题进行形式化，本文研究了两个设置，其中每个设置都有其自己的根期望自由能定义。在第一个设置中，尚未提出任何关于期望自由能的正当化，但所有公式都可以从中恢复出来。然而，在这个设置中，代理不能对观测进行任意先验偏好，只有与生成模型的似然映射相兼容的观测先验偏好的有限类才能赋予。在第二个设置中，已经知道根期望自由能定义的正当化，但该设置仅涵盖两种表达方式，即风险加上不确定性和熵加期望能量的表达方式。

期望自由能的重新框架：四种表述和一个统一

Reframing the Expected Free Energy: Four Formulations and a Unification

We propose a survey of the research contributions on the field of Educational
Timetabling with a specific focus on "standard" formulations and the
corresponding benchmark instances. We identify six of such formulations and we
discuss their features, pointing out their relevance and usability. Other
available formulations and datasets are also reviewed and briefly discussed.
Subsequently, we report the main state-of-the-art results on the selected
benchmarks, in terms of solution quality (upper and lower bounds), search
techniques, running times, statistical distributions, and other side settings.

本文就 “标准” 规划和相应的基准实例进行了教育时间表领域的研究成果调查，找到、评估和讨论了这些规划的主要特点、相关可用数据和最新的成果研究进展。