Grounding ‘Grounding’ in NLP

Findings of the Association for Computational Linguistics: ACL-IJCNLP 2021, pages 4283–4305 August 1–6, 2021. ©2021 Association for Computational Linguistics 4283 Grounding ‘Grounding’ in NLP Khyathi Raghavi Chandu, Yonatan Bisk, Alan W Black Language Technologies Institute Carnegie Mellon University {kchandu, ybisk, awb}@cs.cmu.edu Abstract The NLP community has seen substantial re- cent interest in grounding to facilitate inter- action between language technologies and the world. However, as a community, we use the term broadly to reference any linking of text to data or non-textual modality. In contrast, Cog- nitive Science more formally defines “ground- ing” as the process of establishing what mu- tual information is required for successful communication between two interlocutors – a definition which might implicitly capture the NLP usage but differs in intent and scope. We investigate the gap between these defini- tions and seek answers to the following ques- tions: (1) What aspects of grounding are miss- ing from NLP tasks? Here we present the di- mensions of coordination, purviews and con- straints. (2) How is the term “grounding” used in the current research? We study the trends in datasets, domains, and tasks introduced in re- cent NLP conferences. And finally, (3) How to advance our current definition to bridge the gap with Cognitive Science? We present ways to both create new tasks or repurpose existing ones to make advancements towards achieving a more complete sense of grounding. github.com/khyathiraghavi/Grounding-Grounding 1 Introduction We as humans communicate and interact for a va- riety of reasons with a goal. We use language to seek and share information, clarify misunderstand- ings that conflict with our prior knowledge and contextualize based on the medium of interaction to develop and maintain social relationships. How- ever, language is only one of the enablers of this communication reliant on several auxiliary signals and sources such as documents, media, physical context etc., This linking of concepts to context is grounding and within NLP context is often a knowledge base, images or discourse. Coordination in grounding Purviews of grounding Constraints of grounding Current State What is missing in grounding? • Dynamic grounding • Expanding purviews • Satisfying more media-based constraints Figure 1: Dimensions of grounding – required to bridge the gap between current state of research and what is missing from a more complete sense of grounding. In contrast, research in cognitive science defines grounding as the process of building a common ground based on shared mutual information in or- der to successfully communicate (Clark and Carl- son, 1982; Krauss and Fussell, 1990; Clark and Brennan, 1991; Lewis, 2008). We argue that this definition subsumes NLP’s current working defi- nition and provides concrete guidance on which phenomena are missing to ensure the naturalness and long term utility of our technologies. In Section 2, we formalize 3 dimensions key to grounding: Coordination, Purviews and Con- straints, to systematize our analysis of limitations in current work. Section 3 presents a comprehensive review of the current progress in the field including the interplay of different domains, modalities, and techniques. This analysis …

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