Data modeling is a visual tool for defining data objects and their relationships, called a data schema. A schema defines entities that contain properties. Properties can be values or relationships to other entities. The data modeling tools in Xcode let you create and edit a data model. The data model then becomes a resource that can be loaded and used by your application at runtime.
The user interface for data modeling is almost identical to the interface used for class modeling. The interfaces are so similar that discussion of the common features has been omitted from this chapter. If you haven't read the previous chapter, I strongly urge you to at least browse through the "Class Model Browser," "Class Model Diagram," and "Editing a Class Model" sections. For the most part, simply substitute the words "entity" for "class" and "property" for "member."
To use data modeling effectively, you need to have a basic understanding of Core Data. If you are not familiar with Core Data, a good place to start is the Core Data Programming Guide, which you can find in the Reference Library under Cocoa, Design Guidelines. Or you can browse it online at the
http://developer.apple.com/documentation/Cocoa/Conceptual/CoreData/ web site.
Data modeling is the child of two parents: class modeling and Interface Builder.
The user interface for data modeling is essentially the same as the one used for class modeling, with one very important difference. In data modeling, ...