9. The method according to claim 1 , wherein the data describing the document structure model describe at least one group of items within which at least one other group of items is nested, a group of items describing a structure of the items constituting an element, and at least one of the recordings is associated with each group of items and gives information on the minimum and maximum numbers of occurrences of the group as defined by the document structure model.
9. The method according to claim 1 , wherein the data describing the document structure model describe at least one group of items within which at least one other group of items is nested, a group of items describing a structure of the items constituting an element, and at least one of the recordings is associated with each group of items and gives information on the minimum and maximum numbers of occurrences of the group as defined by the document structure model. 15. The method according to claim 9 , further comprising calculating an actual number of possible types of item for a current item preceding an item to be coded or decoded, which depends on: the minimum and maximum numbers of occurrences, the number of possible types of item within the group and an end-of-group indication, associated with the current item, and the minimum and maximum numbers of occurrences, the numbers of possible types of item able to succeed an item within the group or after the group, and the end-of-group indication, for the groups nesting the current item.