Knowledge graphs (KGs) are inherently incomplete because of incomplete world knowledge and bias in what is the input to the KG. Additionally, world knowledge constantly expands and evolves, making existing facts deprecated or introducing new ones. However, we would still want to be able to answer queries as if the graph were complete. In this chapter, we will give an overview of several methods which have been proposed to answer queries in such a setting. We will first provide an overview of the different query types which can be supported by these methods and datasets typically used for evaluation, as well as an insight into their limitations. Then, we give an overview of the different approaches and describe them in terms of expressiveness, supported graph types, and inference capabilities.

知识图谱是不完全的，因为世界知识不完整且受到输入的偏见影响。本文概述了几种方法，这些方法被提出来以在这种环境下回答查询。首先，我们提供了各种查询类型的概述，这些方法可以支持这些查询类型，并介绍了用于评估的数据集以及它们的局限性。然后，我们概述了不同的方法，并描述了它们的表达能力、支持的图类型和推理能力。

图查询的近似答案