In Room, there are two ways to define and query a relationship between entities: you can model the relationship using either an intermediate data class with embedded objects, or a relational query method with a multimap return type. The turnover is filled with different kinds of things, and it can serve as either a dessert or a mini-meal, depending on its fillings, which can include fruits or meat. Today, even where ER modeling could be useful, it is uncommon because many use tools that support similar kinds of model, notably class diagrams for OO programming and data models for relational database management systems. Others model state changes separately, using state transition diagrams or some other process modeling technique. An ER model is typically implemented as a database. In a relational database a relationship between entities is implemented by storing the primary key of one entity as a pointer or ''foreign key'' in the table of another entity.