Previous questions showed how this can be done with plain tikz. I wonder if it is possible to use tikz drawing library for this purpose.
Here are two previous questions that do this without the use of tikz drawing library: Organisation chart in latex using tikz and Family tree with multiple marriage ties
ׁHow are organizational charts / family trees different from plain graphs? The main difference is that edges are made (mostly) of horizontal and vertical segments; it seems that tikz graph drawing does not support the -| nor the |- edge styles. Yet another difference is that it is common to draw some or all children of a node right below it, as in this gallery example
To clarify, I ask for a method of combining the smart algorithms for graph layout introduced in tikz 3 to produce similar results.
One obvious reason is that although the previous examples produce beautiful output, they do not scale at all. One has to manually design and then implement the layout for each particular instance.
Yet another, perhaps less obvious, reason is that the the family/organizational style can be more compact: vertically stacking children makes it possible to share parent-child edges. Even horizontal stacking is useful since it makes arrows clearer.
It is often the case that you need to squeeze the layout of a given graph to fit within hard page- or other geometric constraints. Employing this style could help.
Finally, yet another style for graph/tree layout could be used for making another visual distinction of trees within trees.
tikzand I am not sure what you mean by the difference between 'plain tikz' and 'tikz drawing library'. In fact the two questions also seem to usetikzlibraries, so you can't mean 'tikz without additional libraries'. There are numerous examples of these kinds of diagrams on this site using all manner of different packages, libraries and methods for drawing them. What is the gap you see which this question is intended to address? – cfr Aug 08 '14 at 18:40