Evaluating and Enhancing Structural Understanding Capabilities of Large Language Models on Tables via Input Designs

Large language models (LLMs) are becoming attractive as few-shot reasoners to solve NL-related tasks. However, there is still much to be learned about how well LLMs understand structured data, such as tables. While it is true that tables can be used as inputs to LLMs with serialization, there lack comprehensive studies examining whether LLMs can truly comprehend such data. In this paper we try to understand this by designing a benchmark to evaluate structural understanding capabilities (SUC) of LLMs. The benchmark we create includes seven tasks, each with their own unique challenges, e.g,, cell lookup, row retrieval and size detection. We run a series of evaluations on GPT-3 family models (e.g., text-davinci-003). We discover that the performance varied depending on a number of input choices, including table input format, content order, role prompting and partition marks. Drawing from the insights gained through the benchmark evaluations, we then propose self-augmentation for effective structural prompting, e.g., critical value / range identification using LLMs' internal knowledge. When combined with carefully chosen input choices, these structural prompting methods lead to promising improvements in LLM performance on a variety of tabular tasks, e.g., TabFact($\uparrow2.31\%$), HybridQA($\uparrow2.13\%$), SQA($\uparrow2.72\%$), Feverous($\uparrow0.84\%$), and ToTTo($\uparrow5.68\%$). We believe our benchmark and proposed prompting methods can serve as a simple yet generic selection for future research. The code and data are released in https://anonymous.4open.science/r/StructuredLLM-76F3.