This paper presents SHIRI-Querying 3 , an approach for semantic search on semi-structured documents. We propose a solution to tackle incompleteness and imprecision of semantic annotations of semistructured documents at querying time. We particularly introduce three elementary reformulations that rely on the notion of aggregation and on the document structure. We present the Dynamic Reformulation and Execution of Queries algorithm (DREQ) which combines these elementary transformations to construct reformulated queries w.r.t. a defined order relation. Experiments on two real datasets show that these reformulations greatly increase the recall and that returned answers are effectively ranked according to their precision.