  The recent advances in Large Language Models (LLMs) have stimulated interest
among researchers and industry professionals, particularly in their application
to tasks concerning mobile user interfaces (UIs). This position paper
investigates the use of LLMs for UI layout generation. Central to our
exploration is the introduction of UI grammar -- a novel approach we proposed
to represent the hierarchical structure inherent in UI screens. The aim of this
approach is to guide the generative capacities of LLMs more effectively and
improve the explainability and controllability of the process. Initial
experiments conducted with GPT-4 showed the promising capability of LLMs to
produce high-quality user interfaces via in-context learning. Furthermore, our
preliminary comparative study suggested the potential of the grammar-based
approach in improving the quality of generative results in specific aspects.
