Structural Diagrams: Package Diagrams

What is a SysML Package Diagram?  Several Different Definitions from the Experts

Package diagram (pkg): A Package diagram is a static structural diagram that shows the relationships among packages and their contents. Package can be stereotyped (customized) for organizing model elements into models, views, model libraries, and frameworks.

The SysML Package diagram is used to define or view the Packages that provide the fundamental organization of the repository. These can include name-spaces and their sub-Packages and other less formally defined groups of elements. The Packages that appear in diagrams can also be viewed in the Browser window and their hierarchy can be navigated by expanding and collapsing the tree. 

The main element that is represented in the Package diagram is the Package itself, with the elements it contains. There are a number of important relationships between Packages, including Dependencies that show that one Package is dependent on one more other Packages. Packages can be organized into a number of different types of hierarchy. 

Main Takeaway: The package diagram shows how the model is organized/decomposed while block definition diagrams shows how the system of interest is organized/decomposed.

In most modeling tools there is a "containment tree" window which shows the package/file structure of the model.  This will usually suffice to explain the decomposition of the model.  Therefore the package diagram is not used all that often because the containment tree efficiently explains the model's structure.

Package diagrams are used for "Start Here" or "Navigation" pages within your model.  It will allow new modelers to more efficiently navigate around the model as the containment tree can be overwhelming to new modelers not familiar with the organization. 

In this example, we see several packages with relationships between them.  Packages are portrayed by the folder icon.  Package diagrams are meant to show how the model is organized rather than how the system is organized.  Package diagrams show the meta-model information. 

In experience, these diagrams are used less than the other diagram types because an experienced modeler can usually get the same information  by looking at the containment tree.  Another reason these diagrams are not built by the modeler that frequently is because normally, a common package structure & methodology is used between business area so these metamodel package diagrams can be placed in libraires and project used by the modeler's project.