Xapian discuss - Jul 2006 - B-Trees (was Re: xapian uses inverted index?)

Folks,

Is the Inverted Index (II) structure built upon a B-Tree? I am trying to
untangle the terms II data structure from the underlying/supporting/initial
structures that are ultimately constructed. e.g. the II is stored in a b-tree
(?).

Which file represents the II? Also it appears from the xapian intro to IR doc
that this is the posting list (is this true?). "For a term, t, there is a
list of documents which it indexes. This is called the posting list of t."

I checked wikipedia, and it describes an II as, "An inverted index is an
index structure storing a mapping from words to their locations in a document or
a set of documents, giving full text search." Does Xapian use the II in
this fashion at all or is this the same thing as you stated below?

Thanks,
OSC

> ----- Original Message -----
> From: "James Aylett" <james-xapian@tartarus.org>
> To: xapian-discuss@lists.xapian.org
> Subject: Re: [Xapian-discuss] xapian uses inverted index?
> Date: Fri, 14 Jul 2006 11:38:52 +0100
> 
> 
> On Thu, Jul 13, 2006 at 03:17:34PM -0800, oscaruser@programmer.net wrote:
> 
> > Been looking the IR docs [http://www.xapian.org/docs/intro_ir.html],
> > but didn't see anything about an inverted index. Is such a
> > datastructure used by Xapian to help relevancy, improve search
> > results or a method to determine context? e.g., "At a simple
level a
> > computerised IR system puts the terms in a direct access, or index
> > file. A term can be looked up and its posting list found."
> 
> Inverted indexes can't really help relevancy and similar (at least, I
> don't see how they can). They're basically a way of quickly
figuring
> out which documents contain which terms efficiently. They're essential
> to practical implementations of the kind of IR system Xapian provides.
> 
> Xapian, in some ways, is just some smart algorithms on top of an
> inverted index.
> 
> J
> 
> --
>
/--------------------------------------------------------------------------\
>    James Aylett                                                  xapian.org
>    james@tartarus.org                               uncertaintydivision.org
> 
> _______________________________________________

-- 
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On Fri, Jul 14, 2006 at 09:20:21AM -0800, oscaruser@programmer.net
wrote:
> Is the Inverted Index (II) structure built upon a B-Tree?
This should answer most of your questions:

http://www.xapian.org/docs/quartzdesign.html 

Cheers,
    Olly