Accessing the class model

We access the class model to create or delete instances or to read or update attribute values. In the process, we may want to select a subset of instances (a restriction) of some class. Or we may want to navigate from one instance across one or more relationships to find a set of related instances. In more complex cases, we may want to select a subset of attributes (a projection). In even more complex cases we may want to grab attributes from multiple classes on a subset of instances connected together across relationships to construct tables. Ultimately we may may reduce all of this relational slicing down into the assignment a single scalar value.

In this manner, a small set of fundamental building block actions can be combined to perform powerful class model access operations. We’ll define those building blocks in this section.

Finding instances

Attribute access

Creation and deletion

Subclass migration