Locates 'nlok.modul' elements, that collectively points to all variants of a certain information module.
Used when the choise of information module variant is dependent on situation, user, or similar. The link might be resolved by the system, if all data required are available to the system, or by the end user himself.
For further explanations, see the HyTime standard (ISO 10744), clause 8.3.2.1.