Model fragments Product structure applied fragment (product) product system Structure system 1.. * implemented module system realDes product fragment subsystem realizes fragment blockgroup fragment block HW-product SW-product Fig. 1.13 A product structure The goal with a product structure is not to describe the system. It is to support information management of an implemented system model, since by introducing a product structure, this model becomes fragmented into smaller information ele- ments. Each fragment is related to the product information element by a fragment relation. The selection of how many levels are needed in a product structure and how many fragments will exist on each level depends primarily on the complexity of the system, and is entirely an information management decision. The top level product of the product structure will be referred to (by the productStructure rela- tion) from the system information element for the implemented system. If there are several variants of implemented systems, they will most likely be integrated in the same product structure. Lower product levels refer to parts of the implemented sys- tem by product names. Naming the levels of the product structure is also an information management decision that has nothing to do with the structure, functions and characteristics of the corresponding concrete systems (described by sysnet models). An example of typical names (module, subsystem, block, etc.) are given in Fig. 1.13. Between lev- els, an upper model fragment is partitioned into smaller fragments that normally 1.5 System Models represent special technical competence, SO that the design responsibility for each lower level fragment can be allocated to some design group that has such special competence. By introducing a product structure, the implemented system model becomes a set of model fragments in a more or less hierarchical structure. The goal of the structure is to support the realization of implemented systems and the provisioning of concrete systems. The defined 