I have tried to illustrate this in the figure above.
Having a wide foundation for traceability is important if the information is to be used for optimization and quality improvement.
I do not think industrial bakeries would have this type of precision, they would probably be satisfied with being able to map from bread type and production day to the raw materials used. And should there be a problem, they are prepared to recall large quantities. However, with more precise traceability information the problem with the oven can be discovered as part of process optimization.
Precision is also diluted if products are recirculated under production. Such phenomenons are sometimes referred to as "silos". Then in theory a particular generation of the production will live on forever in future production. In practice however, such continuous production will be broken into distinct time steps by management routines. But, if you are building a production line from scratch, you may want to spend some time thinking about how to protect investments in precise traceability information.
On the other hand, sometimes it is necessary to loose information in order to be able to make a homogeneous type of product. Consider a factory producing tomato puree. Their customers probably want the "same" product irrespective of where the tomatoes came from. But the tomatoes delivered by farmers may be in varying stages of ripening. So while one batch may be made from perfectly ripened tomatoes, another batch may be based on a blend of unripe and "over-ripe" tomatoes. Hopefully, the producer is so good at this balancing of ingredients that they have the same qualities for all customers. But information about the different farmers is gone.
Each of the participants in the lower part are probably independent companies. Therefore they should each have their own GTNet domain, and share global information through GTNet.
But what happens if two or more of the production lines are owned by the same company? In a corporation goods can be shipped both between daughter companies (internally?) and to independent chain partners. Therefore the goods must have unique identifiers. Each corporation can choose between two extremes to create traceability:
The illustration above shows these two ways of organizing such a ownership of multiple production lines. Each production line is surrounded by a polygon or rectangle, with trade units moving between them. Grey rectangles are used to indicate production lines owned by the same owner. We call the alternative on the right hand side corporate traceability. In the left hand alternative each production line has its own GTNet domain, whereas in the alternative on the right the production lines with the same owner shares a GTNet domain.
There are a number of issues to consider when deciding which alternative to go for. First of all, company organization and ownership may change over time. So one should bear in mind that what you have today may be different tomorrow. In business life mergers and splits reflect changing business strategies and focus. Aspects like the cost of integration and subscription to GTNet are probably of less importance than other business goals. Anyway, letting each production line have its own traceability model allows each to be specialized, while having one for all production lines in the corporation forces this to cover the union of the involved lines.