Please send me some links on how to use NSOutlineView with NSTreeController bindings without using core data.
Here is a useful blog-post, which I wrote, which may prove to be useful: The simplest NSTreeController example
In addition to the documentation, Apple's sample SourceView project should help you better understand things:
"SourceView" is a Cocoa application that demonstrates how to use NSOutlineView driven by NSTreeController and various other Cocoa classes to produce a Finder-like left column source view. Among the key features used to imitate this commonly used view are the use of NSTableViewSelectionHighlightStyleSourceList, NSViewController, NSCollectionView, and WebView.
You can find a simple example of a NSOutlineView datasource in my response to NSOutlineView example