# Choosing a Tree Model

Saxon provides two implementations of the internal tree data structure (or tree model). The tree model can be chosen by an option on the command line (-dt for the tiny tree, -ds for the linked tree [previously known as the "standard tree"]) or from the Java API. The default is to use the tiny tree model. The choice should make no difference to the results of a transformation (except the order of attributes and namespace declarations) but only affects performance.

There is an exception to this: the "linked tree" model (-ds) does not support type annotations. If you use Saxon-SA to annotate element and attribute nodes, use the "tiny tree" (-dt).

Generally speaking, the tiny tree model is both faster to build and faster to navigate. It also uses less space.

The tiny tree model gives most benefit when you are processing a large document. It uses a lot less memory, so it can prevent thrashing when the size of document is such that the linked tree doesn't fit in real memory.

The linked tree is used internally to represent stylesheet and schema modules because of the programming convenience it offers: it allows element nodes on the tree to be represented by custom classes for each kind of element.

If in doubt, stick with the default.

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