Internal Block diagrams and Block Definition diagrams define the system structure and identify the large-scale organizational pieces of the system. They can show the flow of information between system components, and the interface definition through ports. In large systems, the components are often decomposed into functions or subsystems.
Block definition diagrams define the components of a system, the flow of information between components, and have the following parts:
Rational® Rhapsody® automatically creates the Block Definition Diagrams category in the browser and adds the name of the new block definition diagram. In addition, Rational Rhapsody opens the new diagram in the drawing area allowing you to construct the diagram using the Adding graphics to block definition diagrams. As you add blocks and link them to show relationships, you can consider the many uses of blocks described in Block properties and behaviors topic.
A SysML dimension represents a standard physical concept for a set of units. For example, "Length" is a dimension in SysML. that helps you to organize units into comprehensive sets based on the physical domain. Like units, a dimension is used only to set the Dimension property for a Unit or for a valueType, and is never used as a type. Dimensions are typically selected from a standard library model that is a part of the SysML profile.