This section describes how to work in two different types of diagrams that will model a structure of systems: the SysML Block Definition Diagram (BDD) and SysML Internal Block Diagram (IBD). The elements in the BDD are elements of definition, while the elements in the IBD are elements of usage. Elements of definition describe unique instances and can be reused in multiple contexts to share this definition; e.g., the Block is a definition and is used as a type in the IBD. The IBD displays usages of Blocks that are the Part Properties and Reference Properties of the Block. In other words, the Part Properties are the usages of the Block in the context of composing the Block.

Read the following  topics to learn how to model your structure: