shuijian-xu
commented
5 years ago The source system will not share the data warehouse data model and will not be aware of the effect of changes. For instance, in the Wine Club, there is a relationship between the address of a customer and the sales area that contains the address. So it could be said that the address determines the sales area.
Retrospection = true for relationships means that the lifespan of each relationship must be recorded and kept so that the results from queries will faithfully reflect history. An example of this in the Wine Club is the relationship between customer and sales area. If a customer moves from one sales area to another, it is important that the previous relationships of that customer with sales areas are retained.