The data description entities
The smallest data description entity is the Data Element. Data Elements are grouped in Segments, Tables, or Logical Views which are in turn logically grouped into Data Structures. With the Database Block entity, you can describe the different types of databases logically and physically. Finally, you use the Meta Entity to extend the metamodel by describing customized data.
The basic principles of the Rational® Programming Patterns metamodel and the data description entities in the kernel facet are presented in the Data description video.