In order to draw orthogonal edges in flowchart I downloaded and installed the "graphviz-2.27.20101013.0445.msi" package for windows OS. It works very well, one sample is attached.
But when I wanted to add edge label with sentences like: splines="ortho"; ..... A -> B [label="yes"] an memory error occured, snapshot is also attached.
Thus I had to use: A -> B [headlabel="yes"] instead.
Hope someone could fix this problem in next edition.
A -> B [label="yes"]
[erg] Yes, as noted in a post to the mailing list, orthogonal edges still does not handle edge labels in dot and ports.