Under the Hood of Core Data - Core Data - page 3

Figure 2—The data model in grid view
Xcode understands how to compile this file. When Xcode encounters this file
during the compile process of a project, it compiles it into a binary form
ending with the extension .mom . We can also build this file from the command
line using the momc tool.
Editing the Data Model
In Appendix 1, Building a Foundation , on page 209 , we started with a sample
project that already has a data model included. How did we create that data
model? To begin with, we told Xcode to create a new file (File > New > File...),
and we selected Data Model from the template, as shown in Figure 3, Creating
a new data model , on page 4 .
This presents us with a blank data model ready to be edited. From here, in
grid view, we added the three entities being used in the project: Recipe ,
RecipeIngredient , and Type . We then added the attributes and relationships for
each of those entities. For a discussion of entities, attributes, and relation-
ships, take a look at Section 1.4, NSManagedObject , on page 10 .