class

• 
• Represents complex object types. In OO design parlance, such objects are identified with a separate identifier, in contrast to value types whichiare identified by their value.

datatype

• symbol:
  
• Represents a value type. Examples are the primitive types such as integer, real, string, but also higher dimensional points, and certain structured value types.

enumeration

attribute

inheritance

collection/composition

reference

subsets