Important NHibernate terminology

From this chapter onwards, we will be using some terms. These terms have special meanings when used in context of NHibernate or data access layers of applications. It would help to know what these terms mean and how we are going to use them in this chapter and in rest of the book. It is possible that some of these terms are already known to you.

POCO, Plain Old CLR Object. An alternate term for a class in C# which:

• Does not inherit from classes defined in any framework
• Does not implement interfaces defined in any framework
• Does not use any attributes defined in any framework

We will just use the word class most of the time in this book but if I may have to use POCO in a few places, you will know what I mean.

• Entity: A class having an identifier that identifies an instance at least in the entity graph maintained by NHibernate. This may be slightly confusing, but as we progress through the chapter you will know more about NHibernate to understand this clearly. Till that time, whenever I say entity, assume that I am referring to a class/POCO.
• Persistent Class: Any class which NHibernate is able to persist in one or more database tables using the mappings defined.
• Attribute/property: When used in reference to POCO/class, this means getter/setter properties or fields on the class. When used in reference to XML, this would mean usual XML attributes. I may refer to class attributes as properties in some places to avoid confusion.