有谁知道在网上描述Lucene索引格式IN DETAIL的体面文档在哪里？

I am mainly curious as to the inner workings of the engine itself. I couldnt find anything about the index format itself (IE in detail as though you were going to build your own compatible implementation) and how it works. I have poked through the code, but its a little large to swallow for what must be described somewhere since there are so many compatible ports to other languages around. Can anyone provide a decent link?I am mainly curious as to the inner workings of