Hideaki Joko

Hideaki Joko, Faegheh Hasibi

Building conversational agents that can have natural and knowledge-grounded interactions with humans requires understanding user utterances. Entity Linking (EL) is an effective and widely used method for understanding natural language text and connecting it to external knowledge. It is, however, shown that existing EL methods developed for annotating documents are suboptimal for conversations, where personal entities (e.g., "my cars") and concepts are essential for understanding user utterances. In this paper, we introduce a collection and a tool for entity linking in conversations. We collect EL annotations for 1327 conversational utterances, consisting of links to named entities, concepts, and personal entities. The dataset is used for training our toolkit for conversational entity linking, CREL. Unlike existing EL methods, CREL is developed to identify both named entities and concepts. It also utilizes coreference resolution techniques to identify personal entities and references to the explicit entity mentions in the conversations. We compare CREL with state-of-the-art techniques and show that it outperforms all existing baselines.

Hideaki Joko, Faegheh Hasibi

A systematic, reliable, and low-cost evaluation of Conversational Information Access (CIA) systems remains an open challenge. Existing reference-based evaluation methods are proven insufficient for evaluating the dynamic nature of information access conversations, while existing LLM-based reference-free methods suffer from evaluation bias and limited generalizability. This work proposes FACE: a Fine-grained, Aspect-based Conversation Evaluation method that provides evaluation scores for diverse turn and dialogue-level aspects of conversations. FACE leverages beam search and bandit optimization to select optimized LLM instructions per evaluation aspect. It assigns scores to atomic information units (particles) using the selected instructions and then aggregates them into a single score. We show that FACE achieves a strong correlation with human judgments, achieving system correlation of 0.9, outperforming state-of-the-art conversation evaluation methods by a large margin. We further demonstrate its optimized instructions are transferable across various LLMs and datasets. Additionally, unlike existing LLM-based methods that provide single uninterpretable scores, FACE provides insights into the system performance and enables identifying and locating problems within conversations.

Hideaki Joko

Conversational interactions have reshaped information retrieval systems, as users increasingly favour direct answers over traditional hyperlinks. To build reliable Conversational Information Access (CIA) systems that account for personal context, this thesis addresses challenges: (1) personal context extraction, (2) personalized response generation, and (3) effective and interpretable system evaluation. First, we tackle personal context extraction by studying what Entity Linking (EL) in conversations entails, introducing a dataset for conversational entity linking (ConEL), and proposing CREL, a novel EL method tailored for conversational settings. Second, we focus on personalized response generation by proposing LAPS, a method for efficiently constructing large-scale, human-written, personalized conversational datasets, and using them to study how users' preferences can be utilized to generate personalized responses. Finally, we address the need for effective and interpretable system evaluation by introducing FACE, an automatic, reference-free method that assesses entire conversations and aligns closely with human judgments.