Acyclic Graph directory and General Graph Directory

I need a simple explanation or introducti开发者_StackOverflowon for Acyclic Graph directories and General Graph Directories. I Google for it, but the explanations were too technical.

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Acyclic Graph Directories:

• Allow directories to link to one another, allow multiple directories to contain same file i.e., only one copy of the file exists and any change in the file can be viewed by all directories in which it is contained.
• Results in Acyclic graphs
• Two users can name same file or same directory
• Duplicate paths may complicate task of backing up periodically

General Graph Directories:

• Allow cycles
• More flexible
• More costly
• Need garbage collection (circular structures)
• There could be a subset of directories all with reference count > 0, but none of these are reachable from the root