What is the best representation of parsed XML?

Hi Folks,

In a compiler book [1] that I am reading it shows two approaches to representing a parsed program: (1) as a parse tree, and (2) as a sequence of Three Address Code (TAC) instructions. Surprisingly (to me) the book recommends TAC:

"TAC is much more flexible than tree representations when it comes to performing optimizing transformations on the code. It is recommended that compilers that are intended to perform optimization use TAC as their intermediate representation."

What are the representations for parsed XML? I am familiar with two representations:

1. Parse tree, e.g., DOM
2. Sequence of event messages, e.g., SAX

Are there other representations?

Have you found a representation that is especially efficient for your processing applications?

/Roger

[1] "Introduction to Compiling Techniques" by J.P. Bennett, page 164.