Is there any detailed explanation or description offered for what the Dirokimes are?
In A Fire Upon the Deep, two characters are introduced on the Ølvira that are described as Dirokimes, Glimfrelle and Tirolle. Little is given by way of explanation as to exactly what Dirokimes are, although they are mentioned other places in the book.
We know they are described as a race, have something called "longfingers", seem to travel primarily (exclusively?) in pairs of brothers and sisters, were living on Sjandra Kei in something described as "dream habitats", and do not exist elsewhere this side of the Transcend.
Presumably they are aliens, although I suppose an altered line of humans could be possible.
Is there an explanation given, or further description, in anything else by Vernor Vinge, published or unpublished?