There's more such technology out there. If you're really interested in
compression have a look at what bzip does (yes, it's a "B" instead a "G").
There are many ways in which you can improve performance if you've got
knowledge about structuring and what kind of dictionaries to use. LZ77 is
just an excellent and fast general purpose algorithm.

  - Andreas

> -----Original Message-----
> From: Richard A. O'Keefe [mailto:ok at atlas.otago.ac.nz]
> Sent: Monday, June 05, 2000 5:07 PM
> To: squeak at cs.uiuc.edu
> Cc: recipient list not shown
> Subject: RE: Cheap updates
> 
> 
> A recent issue of SIGMOD Record had an article about XMill,
> a compressor for XML.  It gets rather better compression than
> gzip does, despite being built atop gzlib.
> 
> How come?
> 
> To the extent that I understand it, by splitting the input stream into
> tree and contents, then partitioning the contents by context, then
> compressing the contextualised contents with gzlib.  The key idea here
> is that similar parts of the tree can be moved together to compress
> better.
> 
> While FileOuts and ChangeSets are not XML, they are none-the-less
> structured, and it is plausible that e.g. splitting structure, method
> bodies, and comments and compressing them separately might do 
> very well.
> 
> What would happen, for example, if the compression dictionary were
> "primed" with class and instance variable names before compressing
> each method?
>