How to add UML constraint between two edges?

Question

It's about "edge between edges" like in the picture here: http://www.uml-diagrams.org/class-diagrams/class-constraint-dashed.png --- currently I add to labels to these edges, convert them manually to nodes, and then draw an edge between those nodes (they're empty), but this is ugly work-around rather than proper solution. I'd expect the possibility to connect two nodes of edges (and by the node I mean an additional node, that one adds to an edge to make curved lines) --- this would give 100% control over where the connecting edge is placed. This, however, could bring possible problems for layout algorithms (one easy solution is probably to ignore it while calculating new layout).

Is there any change for this option?

Answer 1

What you call a "node, that one adds to an edge to make curved lines" is called a "bend" in diagramming terminology. The "Account", "Person", and "Corporation" elements in your sample diagram are "nodes".

With the terminology clarified, let us continue to your actual issue. You cannot connect edges to other edges or bends to bends in other edges. I am pretty sure that we will not add such a feature to yEd, because the strict adherence to the formal graph model (i.e. an edge always connects either one node to itself or connects exactly two nodes) is a very important requirement for almost all feaures in yEd.

The best you can do to achieve the visualization shown in your sample diagram, is to split the edges from "Account" to "Person" and "Account" to "Corporation" into two distinct edges each. To do that, create a black size 1 node, add said node to a custom palette section, then drop the corresponding node template from the palette onto the edge you want to split. Once you have inserted these split nodes, you can connect the split nodes with an additional edge.