The present invention concerns a method and device for coding or decoding a structured document, for example an XML document, using a structure-describing file of the XML Schema type.The method comprises a step of configuring an encoder or decoder including the obtaining of data describing a document structure model and their storage in the form of recordings, and a step of calculating a number of items, referred to as “possible items”, able to succeed, according to the structure model, an item of said model, said number of possible items being stored in a recording associated with said item. In order to facilitate calculations, the recordings comprise the minimum and maximum numbers of occurrences of the item defined by the structure model.