  We present an Open-Vocabulary 3D Scene Graph (OVSG), a formal framework for
grounding a variety of entities, such as object instances, agents, and regions,
with free-form text-based queries. Unlike conventional semantic-based object
localization approaches, our system facilitates context-aware entity
localization, allowing for queries such as ``pick up a cup on a kitchen table"
or ``navigate to a sofa on which someone is sitting". In contrast to existing
research on 3D scene graphs, OVSG supports free-form text input and
open-vocabulary querying. Through a series of comparative experiments using the
ScanNet dataset and a self-collected dataset, we demonstrate that our proposed
approach significantly surpasses the performance of previous semantic-based
localization techniques. Moreover, we highlight the practical application of
OVSG in real-world robot navigation and manipulation experiments.
