1. Method for compressing and decompressing a structured document, associated with at least one tree structure schema ( 1 ; 31, 39, 43 ) defining a structure of the document and including nested structure elements ( 32, 33, 34, 40, 44, 45, 46, a3, a4, X, Y, a1, a5, a1, a2, A, B) representing data sets of the document, the structure elements being distributed in three categories, namely structured root elements ( 31, 39, 43 ), groups of elements ( 32, 33, 34, 40, 44, 45, 46 ), and structured (X, Y, A, B), or unstructured (a3, a4, a1, a5, a1, a2) base elements corresponding to the lowest level elements in the structure, each base element being associated with an information type, characterized in that at least one information type of the base elements is first associated with an adapted compression algorithm ( 16 ), the method including the following steps: performing a syntactic analysis ( 11 ) of the document's structure schema, compiling ( 13 ) the normalized structure schema to obtain one finite automaton ( 5 ) per root element, each automaton including states (“0”, “1”, to “n”) interconnected by transitions (“m1”, “m2”, to “mn”) respectively representing the structure elements, and compressing ( 15 ) the structured document ( 2 ) for compression including executing the finite automata ( 5 ) on the document, and executing the compression algorithm ( 16 ) when a data set having an information type associated with said algorithm is encountered in the structured document ( 2 ).