I was reminded of the Qeng Ho, both historic (http://en.wikipedia.org/wiki/Zheng_He http://en.wikipedia.org/wiki/Zheng_He) and fictional (http://en.wikipedia.or

I was reminded of the Qeng Ho, both historic (http://en.wikipedia.org/wiki/Zheng_He http://en.wikipedia.org/wiki/Zheng_He) and fictional (http://en.wikipedia.org/wiki/A_Deepness_in_the_Sky http://en.wikipedia.org/wiki/A_Deepness_in_the_Sky). Vernor Vinge describes a universe where civilizations rise and fall throughout the galaxy, and a race of space-faring traders ensure that technological advances aren't lost when civilizations die.