Understanding the fundamentals of building an in-Memory Distributed Graph I am working on a project where I have to build an in-memory distributed graph capturing the relation between similar files(based on some similarity metric) stored in shared file system over multiple nodes in a network.

I know basic graph data structure. I googled to know about distributed graph, but what I found mostly is just an info about existing distributed graph databases like titan, FlockDB etc. But I really couldn't find any fundamental guide to building a distributed graph or in general explaining a basic algorithm of building a distributed graph.

Can you please suggest few references where I can get such material explaining the fundamentals.
You should look at the Cloud Computing area - there is a lot of research about graphs representation and processing there.

For example, this paper.