Which postgres design for a nested resource that can link to the same type of resource
Two methods of querying hierarchical data:


Ltree. You can see an example of me using it in a similar question here.. The problem with ltree is you have to serialize the relationship yourself. It's a flat table. This is a pita. Updating it also kind of sucks.
Self-referencing table. You can see an example of me using it in a similar question here.. This is probably ideal because you're only storing the identifier of the parent. This create a simple hierarchical data type that you can query with a RECURSIVE CTE. 


Example table,

CREATE TABLE foo (
  idfoo          serial    PRIMARY KEY
  idparent       int       REFERENCES foo
  description    text,
  key            text,
  restriction    text,
  title          text,
  default        text
);


Then you insert your root, and your children which point to the parent.