All references can be found at:
http://www.omg.org/technology/documents/modeling_spec_catalog.htm
M3 = Meta-metamodel
M2 = Metamodel
M1 = Model (some class diagrams)
M0 = Model instance (some object diagrams)
MOF = Meta Object Facility
CWM = Common Warehouse Metamodel
MDA = Model Driven Architecture
Profiles = mechanisms used to tailor UML to Java, C++, XML, EJB, CORBA, or domain models.
The core bootstraps the rest of the system:
Boolean
Integer
String
UnlimitedNatural
A model consists of many elements.
An element may have a name.
An element may own other elements and be owned by an element.
A type is an element.
An element may have a type.
Classifiers and features are elements.
A classifier owns many features.
A relationship is an element.
A relationship relates one or more elements.
A directed relationship relates a source element with one or more target elements.
A data type is a type.
A data type may be a primitive type or an enumeration.
A package is an element that contains other elements.
A class is a type with properties, operations, and super classes.
Classes and associations are classifiers.
Classes and associations have properties.
An instance of a class is called an object.
An instance of an association is called a link.