We present a system based on a Bayesian Network formalism for structured documents retrieval. The parameters of this model are learned from the document collection (documents, queries and assessments). The focus of the paper is on an algebra which has been designed for the interpretation of structured information queries and can be used within our Bayesian Network framework. With this algebra, the representation of the information demand is independent from the structured query language. It allows us to answer both vague and strict structured queries.