From 339167a0c9b34b27a97e6e76b88adfc8d0f9232a Mon Sep 17 00:00:00 2001 From: Dan Winship Date: Wed, 1 Mar 2000 19:37:47 +0000 Subject: add an Ibex whitepaper svn path=/trunk/; revision=1999 --- doc/white-papers/mail/ChangeLog | 4 + doc/white-papers/mail/ibex.sgml | 158 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 162 insertions(+) create mode 100644 doc/white-papers/mail/ibex.sgml (limited to 'doc') diff --git a/doc/white-papers/mail/ChangeLog b/doc/white-papers/mail/ChangeLog index 6d4e8b7f8a..5933582d40 100644 --- a/doc/white-papers/mail/ChangeLog +++ b/doc/white-papers/mail/ChangeLog @@ -1,3 +1,7 @@ +2000-03-01 Dan Winship + + * ibex.sgml: Ibex white paper + 2000-02-29 Dan Winship * camel.sgml: Reorg a bit more, make the 
 section narrower,
diff --git a/doc/white-papers/mail/ibex.sgml b/doc/white-papers/mail/ibex.sgml
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+Evolution">
+
+
+]>
+
+

+
+  
+    Ibex: an Indexing System
+
+    
+      
+	Dan
+	Winship
+	
+	  

+	    danw@helixcode.com
+	  

+	
+      
+    
+
+    
+      2000
+      Helix Code, Inc.
+    
+
+  
+
+  
+    Introduction
+
+    
+      &Ibex; is a library for text indexing. It is being used by
+      &Camel; to allow it to quickly search locally-stored messages,
+      either because the user is looking for a specific piece of text,
+      or because the application is contructing a vFolder or filtering
+      incoming mail.
+    
+  
+
+  
+    Design Goals and Requirements for Ibex
+
+    
+      The design of &Ibex; is based on a number of requirements.
+
+    
+      
+        
+	  First, obviously, it must be fast. In particular, searching
+	  the index must be appreciably faster than searching through
+	  the messages themselves, and constructing and maintaining
+	  the index must not take a noticeable amount of time.
+	
+      
+
+      
+        
+	  The indexes must not take up too much space. Many users have
+	  limited filesystem quotas on the systems where they read
+	  their mail, and even users who read mail on private machines
+	  have to worry about running out of space on their disks. The
+	  indexes should be able to do their job without taking up so
+	  much space that the user decides he would be better off
+	  without them.
+	
+
+	
+	  Another aspect of this problem is that the system as a whole
+	  must be clever about what it does and does not index:
+	  accidentally indexing a "text" mail message containing
+	  uuencoded, BinHexed, or PGP-encrypted data will drastically
+	  affect the size of the index file. Either the caller or the
+	  indexer itself has to avoid trying to index these sorts of
+	  things.
+	
+      
+
+      
+        
+	  The indexing system must allow data to be added to the index
+	  incrementally, so that new messages can be added to the
+	  index (and deleted messages can be removed from it) without
+	  having to re-scan all existing messages.
+	
+      
+
+      
+        
+	  It must allow the calling application to explain the
+	  structure of the data however it wants to, rather than
+	  requiring that the unit of indexing be individual files.
+	  This way, &Camel; can index a single mbox-format file and
+	  treat it as multiple messages.
+	
+      
+
+      
+        
+	  It must support non-ASCII text, given that many people send
+	  and receive non-English email, and even people who only
+	  speak English may receive email from people whose names
+	  cannot be written in the US-ASCII character set.
+	
+      
+    
+
+    
+      While there are a number of existing indexing systems, none of
+      them met all (or even most) of our requirements.
+    
+  
+
+  
+    The Implementation
+
+    
+      &Ibex; is still young, and many of the details of the current
+      implementation are not yet finalized.
+    
+
+    
+      With the current index file format, 13 megabytes of Info files
+      can be indexed into a 371 kilobyte index file—a bit under
+      3% of the original size. This is reasonable, but making it
+      smaller would be nice. (The file format includes some simple
+      compression, but gzip can compress an
+      index file to about half its size, so we can clearly do better.)
+    
+
+    
+      The implementation has been profiled and optimized for speed to
+      some degree. But, it has so far only been run on a 500MHz
+      Pentium III system with very fast disks, so we have no solid
+      benchmarks.
+    
+
+    
+      Further optimization (of both the file format and the in-memory
+      data structures) awaits seeing how the library is most easily
+      used by &Evolution;: if the indexes are likely to be kept in
+      memory for long periods of time, the in-memory data structures
+      need to be kept small, but the reading and writing operations
+      can be slow. On the other hand, if the indexes will only be
+      opened when they are needed, reading and writing must be fast,
+      and memory usage is less critical.
+    
+
+    
+      Of course, to be useful for other applications that have
+      indexing needs, the library should provide several options, so
+      that each application can use the library in the way that is
+      most suited for its needs.
+    
+  
+

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