The invention provides a computer-implemented method and system intended for designing an assembly of a plurality of objects. The assembly is modeled by a directed acyclic modeling graph having nodes and arcs. Each node represents an object of the assembly. Each arc represents the use of an end node by an origin node. At least one arc is uniquely identified by an identifier. The assembly is further modeled by at least one relation having at least one tuple containing a first chain of at least one identifier. The method comprises determining at least one mapping between the first chain and a second chain of at least one identifier as well as substituting at least one occurrence of the first chain in the tuple of the relation with the second chain. The invention provides a means to repair broken tuples automatically and thus to facilitate design.