The Sellar problem is an analytical multi-disciplinary design problem. The objective function f is to be minimized with
 respect to the variables z1, z2 and x1 while being subjected to g1, g2 and the disciplines y1 and y2.

D1: y1 = z1^2 + x1 + z2 -0.2*y2
D2: y2 = y1^0.5 + z1 + z2
F1: f = x1^2 + z^2 + y1 + e^(-y2)
G1: g1 = y1/3.16 - 1
G2: g2 = 1 - y2/24

More information on the Sellar problem can be found in literature, e.g. on:
https://arc.aiaa.org/doi/abs/10.2514/6.1996-714, 
https://www.researchgate.net/publication/2759746_Response_Surface_Based_Concurrent_Subspace_Optimization_For_Multidisciplinary_System_Design or
http://openmdao.org/releases/0.2.5/docs/mdao/intro.html

The files in the subdirectories represent and illustrate Repository Connectivity Graphs (RCGs), Fundmental Problem
Graphs (FPGs) and MDO Data/Process Graphs (MDG/MPG). These graphs were developed for a new software system called
KADMOS.

In the RCG files two additional tools, D3 and G3, are present. They are consequently removed for the FPG files and
demonstrate the KADMOS capabilities of tailoring a larger database down to a specific problem.