A topic diagram is a non-editable, query-based diagram that you can use to view the existing relationships between elements in your model. A topic diagram displays a specific set of relationships between a group of given elements. The set of relationships, or the topic, defines the parameters of the query for the diagram.
The query and the context that you specify persists in the topic diagram. Each time that you open a topic diagram, the system queries the underlying elements and automatically populates the diagram with the latest results. However, if you make changes to the underlying model when a topic diagram is open, the topic diagram might not fully represent the current status of the model until you manually refresh the diagram.
You can select either a default or radial layout format for the topic diagram. The default layout shows all diagram elements in a hierarchy that can span several levels. The radial layout positions the selected diagram element that you used in your query as the hub, or context diagram element. Each diagram element is connected either directly or indirectly to this one context element. The radial layout provides a view to all directly related diagram elements and spans one or two levels.
A topic diagram is similar to a browse diagram except that you can save a topic diagram and reopen it at any time. Unless you save a topic diagram as an editable diagram, you cannot add or modify the diagram elements.