A model is a representation of a problem domain and software system. A model contains classes, logical packages, objects, operations, component packages, components, processors, devices, and the relationships between them. Each of these model elements has model properties that identify and characterize them.
A model also contains diagrams and specifications that provide a means of visualizing and manipulating the model's elements and their model properties. Because diagrams are used to illustrate multiple views of a model, icons representing a model element can appear in none, one, or several of a model's diagrams. This enables you to control which elements and model properties appear on each diagram.
Rational Rose creates .mdl files and Rational XDE creates .mdx files. You can integrate a Rational RequisitePro project with either type of file, but the integrations are separate and provide distinct capabilities.