Modeling use cases and patterns
This chapter introduces the use of E-R diagrams to represent conceptual and logical data models in data engineering projects, but we have seen that the same modeling concepts are also used to design data models for applications and everywhere we want to describe how different pieces of data are related.
In the next sections, we will present a few common use cases of data structures and their models, some known problematic cases, and finally, we point to the whole area of data model libraries.
Header-detail use case
One of the ubiquitous cases when working with data is the header-detail data structure. It is so common that I am pretty sure you have already seen it somewhere.
As an example, it is used in invoices and orders, and almost anywhere else where there is one document with multiple lines of detail inside. The common document info goes into the header entity with the detail lines represented by one or more weak entities depending on...
