CHAPTER Modeling Structure with Blocks 7 This chapter addresses modeling the structure of systems in terms of their hierarchy and inter- connection. It describes blocks--the principle structural construct of SysML--and the two types of diagrams used to represent structure--the block definition diagram and the internal block diagram. These representations are a formalization of traditional systems engineering block diagrams to enable a more precise representation of interfaces, and other aspects of system structure. Note that this chapter includes significant changes to ports that were introduced in SysML, version 1.3. Section 7.1 includes an overview of the changes and Section 7.9 describes the features that have been deprecated in this version. 7.1 OVERVIEW