Plan-Grounded Large Language Models for Dual Goal Conversational Settings
Diogo Glória-Silva, Rafael Ferreira, Diogo Tavares, David Semedo, João Magalhães
TL;DR
The paper tackles dual-goal mixed-initiative conversations where an LLM must ground dialogue in a procedural plan while also handling user instructions. It introduces PlanLLM, a plan-grounded model that can navigate procedural steps, answer plan-grounded questions, handle open requests, and enforce safety norms, trained via multi-objective supervision and Direct Preference Optimization (DPO). A large-scale, real-world augmented dialogue dataset is created to fuel training, combining plan-focused data with context and tone conditioning. Experiments demonstrate that PlanLLM (notably the Vicuna-DPO variant) achieves a 2.1x improvement over strong baselines and generalizes well to unseen domains, such as DIY, while maintaining safety and user satisfaction. The work offers a practical pathway to robust, goal-directed conversational systems that can guide users through complex tasks with guardrails and adaptable behavior.
Abstract
Training Large Language Models (LLMs) to follow user instructions has been shown to supply the LLM with ample capacity to converse fluently while being aligned with humans. Yet, it is not completely clear how an LLM can lead a plan-grounded conversation in mixed-initiative settings where instructions flow in both directions of the conversation, i.e. both the LLM and the user provide instructions to one another. In this paper, we tackle a dual goal mixed-initiative conversational setting where the LLM not only grounds the conversation on an arbitrary plan but also seeks to satisfy both a procedural plan and user instructions. The LLM is then responsible for guiding the user through the plan and, at the same time, adapting to new circumstances, answering questions, and activating safety guardrails when needed. We propose a novel LLM that grounds the dialogue on a procedural plan, can take the dialogue initiative, and enforces guardrails on the system's behavior, while also improving the LLM's responses to unexpected user behavior. Experiments in controlled settings and with real users show that the best-performing model, which we call PlanLLM, achieves a 2.1x improvement over a strong baseline. Moreover, experiments also show good generalization to unseen domains.
