Custom Data Structures

I think data structures are kind of generic. So they're not specific to a particular use case. A model is really a specific, you know, implementation or application of a data structure. I generally wouldn't do it for performance reasons. It's usually because the shape of your data just doesn't naturally fit into one of those patterns. In particular, I often find that I want something like an ordered set,. Or quite often you want a tree structure for things like a view hierarchy and so on.