1. A method of syntactically analyzing a bit stream containing data which have a structure and contents according to a certain format, said method being ntended to generate a tree-like representation of said stream, characterized in that said method comprises: A) reading a schema which, for generically describing said format: a) defines one or more types of data which may contain one or more facets, notably: when said format uses binary words of predefined length or lengths;, one or more types of data corresponding to said binary words of predefined length or lengths, said types of data having at least one facet relating to said length and, when said binary words of predefined lengths may contain one or more padding bits, said types of data having a facet relating to said padding bits, when said format uses binary segments of indefinite length which have contents intended to be imported in said representation by using a certain import mode: a type of data corresponding to said binary segments, said type of data having at least one facet relating to said import mode and, when said binary segments are defined by a stop flag, said type of data having one facet relating to said stop flag, b) comprises a plurality of elements for which it describes a name, a type of data, an interleaving, a predefined or random order and number of occurrences, the occurrence of an element being mandatory or optional, c) when said format provides that data situated at the front of said bit stream give information about the structure or the contents of the rest of said bit stream, defines one or various variables constituted by an access path in said tree-like representation to said data situated at the front, and comprises one or more conditional branches for describing various possible structures or contents as a function of the value of said variable or variables, B) searching in said bit stream for the data that correspond to the elements contained in said schema, C) generating an instance of said schema which contains the data found in said bit stream and which constitutes said tree-like representation.