  In this report, we unify two quite distinct approaches to information
retrieval: region models and language models. Region models were developed for
structured document retrieval. They provide a well-defined behaviour as well as
a simple query language that allows application developers to rapidly develop
applications. Language models are particularly useful to reason about the
ranking of search results, and for developing new ranking approaches. The
unified model allows application developers to define complex language modeling
approaches as logical queries on a textual database. We show a remarkable
one-to-one relationship between region queries and the language models they
represent for a wide variety of applications: simple ad-hoc search,
cross-language retrieval, video retrieval, and web search.
