Expanded Relationship Items
Except for the comment link, connectors can be seen as result of expanded relationship items. Relationship items are generated in pairs for the same relationship, one item in each shape part of the relationship. When you drag and drop one outside its shape, it gets expanded into a connector, with the other reverse item auto-expanded as well. Collapse the connector by selecting and removing the link, and related items will reappear into their shapes.
Connectors may have a plain or dashed line. Dash line tells us we have an optional or to-zero relationship. You may have one item on one side of the relationship with no related item at the other end. Connector’s ends may also represent a fork, in which case they have a to-many cardinality in that direction, contrary of to-one.
Straight Line Connectors
Double-click on a connector to instantly switch its status, from straight to orthogonal and back to straight.
Show Simplified shows connector as plain straight lines. This is convenient in topological or graph models, where people are usually interested in a simple image focused on inter-connectivity. Here is for instance a simple graph model:
What about Crow’s Foot Notation?
We tried to keep on purpose connector’s representation to a minimum, to show only the required elements (like optional and to-one/many) and nothing more. Database administrators and programmers may be more familiar with Crow’s Foot Notation for database models, but it has redundant and “verbose” elements that make the diagram more complex and harder to understand by novice users. We tried on purpose to come up with something in between and hope this will make everyone happy.