Work, Book, and Author Identifiers

First, the new XML API is awesome (I commented so in the blog entry as well). Now I have a couple questions about identifiers. Is this about right:
* book id (found at end of a URL when viewing a book, and in the Tab-del. export): Represents the instance of the book (i.e., edition, as opposed to the work)
* work id (found immediately after 'work' when viewing a book): Represents the work
* author id (not sure where this is found, only saw it in returned data): Identifies the author

You also have the concept of "codes" vs. id's, which seem to be unique identifiers for authors (e.g., twainmark)

So, for example:
http://www.librarything.com/work/3093889/details/33854591
* book id = 33854591
* work id = 3093889
* author code = twainmark

Is this accurate? (If so, I'd be happy to post somehthing like this in the wiki...

Book id - Yes, this represents the instance of the particular book in somebody's library. Editions are one step up from that though. So we have book--&mt;edition--&mt;work.

Work id Yes, exactly right.

Authorid Right now we have not fully transitioned over to author ids. You can see the authorcode on each page though ('hollandchristopher' or 'rowlingjk' in the URL) and you can use that for the time being. Unfortunately author codes are not unique identifiers of an author (which is why we have to have the disambiguation notices on some author pages). We plan on transitioning over to author id numbers for all author designations (hopefully soon). So, in planning for the future, author ids will be returned with all Web services data.

If you have the author ID then it is best to use it (so as to future-proof your code). But if you only know the authorcode then use it.

I'll be adding some extra methods soon for finding book, work, and author information.