i F acet S um: Coreference-based Interactive Faceted Summarization for Multi-Document Exploration (2021)

Abstract: We introduce iFᴀᴄᴇᴛSᴜᴍ, a web application for exploring topical document collections. iFᴀᴄᴇᴛSᴜᴍ integrates interactive summarization together with faceted search, by providing a novel faceted navigation scheme that yields abstractive summaries for the user’s selections. This approach offers both a comprehensive overview as well as particular details regard-ing subtopics of choice. The facets are automatically produced based on cross-document coreference pipelines, rendering generic concepts, entities and statements surfacing in the source texts. We analyze the effectiveness of our application through small-scale user studies that suggest the usefulness of our tool.

## introduction an information consumer aspiring to explore a new topic will often be faced with an extensive collection of texts from which to acquire knowledge. confronted with these texts, the reader would have difficulty determining where to start reading and obtaining details about specific aspects of the topic. addressing this we present ifacetsum, illustrated in figure 1 , an interactive faceted summarization approach and system for navigating within a large input document-set on a topic. the system initially provides a full high-level overview of the topic at a glance in the form of facets. a user can then dive further into subtopics of interest and obtain concise facet-based summaries, capturing the valuable information of a subtopic. the challenge of knowledge navigation has been addressed with various solutions, mainly under the umbrella of exploratory search @xcite tasks. for example, in complex interactive question answering (ciqa) @xcite and conversational qa @xcite , a user interacts with a qa system in order to meet an information need on the source text(s). interactive information retrieval @xcite and conversational search @xcite refine document retrieval through different means of textual interaction. both tasks do not offer a preliminary outline of the source documents, and hence expect a user to formulate queries or questions without system guidance. furthermore, short answers, such as those output in conversational qa, may be insufficient, while lists of relevant textual results, such as in conversational search, may be overwhelming and provoke an inefficient navigation process. as a midpoint solution, interactive summarization provides an initial summary as an overview of the topic, and the ability to inquire, via suggested or free-text queries, for more information in the form of summary expansions (e.g. @xcite . here still, the initial summary, along with the suggested queries, do not produce the full high-level picture, and therefore hints only partially at the possible subtopics that the user might want to explore. we conduct usability studies on our system, and demonstrate its utility for easy navigation in topical document sets, while enabling deep diving into desired knowledge without losing the context of the exploration process. we next describe ifacetsum's interface in §2 and its backend implementation in §3. this is followed by the description and results of our usability investigations in §4, an overview of related work in §5, and finally conclusions and suggestions for future work in §6. ## backend algorithms as portrayed in §2, ifacetsum supports two central features: presenting a faceted navigation panel and generating a summary around selected facetvalues. we next describe how facet-values are generated using cd coreference resolution ( §3.1), and how we apply abstractive summarization, based on a facet-value selection ( §3.2). figure 2 illustrates the entire process. ## related work attaining information of interest from large document sets has been approached with different techniques. a vast amount of research has been conducted on multi-document summarization, as a method for presenting the central aspects of a target set of texts (e.g. @xcite @xcite , where query-focused summarization @xcite biases the output summary around a given query (e.g. @xcite @xcite . recognizing the need for dynamically acquiring a broader or deeper scope of the source texts, exploratory search @xcite was coined as an umbrella term for allowing more dynamic interactive exploration of information. adapting the summarization paradigm to the exploratory setting, interactive summarization enables a user to refine or expand on a summary via different modes of interaction. for example, @xcite and @xcite provide a limited (or no) initial summary on the document set, and support iterative interaction, via queries or preference highlights, to update the summary. however, the succinct initial summary, possibly accompanied by few suggested queries, do not display the full scope of the source texts, which limits the user's perception of the many available sub-topics to learn more about. on the other hand, other exploratory search approaches do provide a more elaborate overview of the source data through sophisticated dashboards or facets of extracted information or metadata (e.g. @xcite @xcite . indeed, faceted navigation @xcite is an effective instrument for navigating within a large data source @xcite . while most faceted search systems generate facets from semi-or fully-structured data, as prominently encountered in e-commerce websites and in research @xcite , some works generate facet hierarchies from unstructured open-domain texts. for example, from product reviews, @xcite extract product aspects and present several summaries, each focused on a single aspect as a "facet", in a form of single-level faceted search. @xcite devise facetvalues from scientific articles by eliciting unstructured textual information (topics, entities) from the articles and their structured metadata (e.g article authors). although these search tools offer a more comprehensive overview of the source data, they either present raw-text search results or do not allow thorough navigation. ## conclusion and future work in this paper, we presented ifacetsum, a novel text exploration approach and tool over large document sets, which incorporates faceted search into interactive summarization. its faceted navigation design provides a user with an overview of the topic and the ability to gradually investigate subtopics of interest, communicating concise information via multi-facet abstractive summarization. fine-grained facet-values are generated from the source texts based on cross-document coreference pipelines. small-scale user studies suggest the utility of our approach for exploring a new topic from multiple documents. future work may speed up the coreference-based facet extraction pipeline, allowing for real-time processing of ad-hoc document sets, and may investigate further methods for facet generation. additional search techniques might be integrated into the exploration scheme, including free text searching as raised in the user study. it would also be appealing to try adapting the system to domains other than news, such as the medical or scientific domains, for which exploration tools would be very useful. such adaptations would depend on the portability of the underlying technologies of cross-document coreference resolution and proposition alignment. finally, future work may explore additional ways of leveraging the power of recent proposition alignment methods.