While much of the research that I did in the past revolved around formal aspects of knowledge representation formalisms, since the start of the 21st century my research has been focused on algorithms and models for intelligent information access.

Life without search engines has become unthinkable. My work in information retrieval is characterized by three broad strands of research: analysis (of collections, documents, queries, and behavior), synthesis of the outcomes of various analyses into a high-quality ranking of search results, and evaluation methodology. In my work I combine theoretical contributions to information retrieval, in terms of new analysis and synthesis algorithms with large-scale evaluations and valorisation activities in collaboration with external partners, both academic, industrial and governmental.

In recent years, my most important contributions in terms of algorithmic analysis of information have to do with effective search methods for social media, recognizing semantic structure in noisy text sources, click models for explaining user behavior, and robust methods for recognizing subjective aspects of information (such as sentiment, personality, reputation). Part of this work is being carried in collaboration with colleagues the humanities and social sciences.

My work on synthesizing the outcomes of these types of analysis has revolved around fusion methods and aggregated search over large numbers of sources, semantic search (where heterogeneous information related to meaningful units such as people, events or cultural artefacts are gathered and made searchable), and algorithms for self-learning search engines that automatically improve the quality of their combined results through interactions with users.

As to evaluation, I have recently worked on methods for automatically generating training material for learning to rank, on using graphical models that capture user behavior to create model-based metrics, and on the foundations of effective online models for determining the quality of ranking algorithms from implicit signals.

Please consult the web site of my research group for details on research projects that I am currently involved with.