xml-dev - RE: RFC: Attributes and XML-RPC

["Julian Reschke" <reschke@medicaldataservice.de>]

I find this way surprising. Yes, it's clear that opening and closing tags compress well, but I would still have expected the attribute version to be smaller...

 

--
Julian F. Reschke (mailto:reschke@medicaldataservice.de)
MedicalData Service GmbH Münster, Germany

-----Original Message-----
From: owner-xml-dev@ic.ac.uk [mailto:owner-xml-dev@ic.ac.uk]On Behalf Of Mark Nutter
Sent: Wednesday, September 22, 1999 7:26 PM
To: xml-dev@ic.ac.uk
Subject: RE: RFC: Attributes and XML-RPC

At 12:16 PM 09/22/99 -0400, Hunter, David wrote:

So even if you
compress the files, the attribute version will be able to compress to 50%
smaller than the other file.  Again, 2KB isn't a lot, but if we're talking
megabytes in size, 50% is a lot.

I wrote a quick perl script to take /usr/dict/words and turn it into an XML file, with some artificially generated "attributes".  In the resulting file named attrib.xml, each <word> tag contains the additional information as attributes.  I did the same thing to produce a file called child.xml, except that the additional information is presented as a child element instead of as an attribute.  Here are the results:

$ ./make.pl
$ ls -l
total 13004
-rw-rw-r--   1 mnutter  mnutter   5811852 Sep 22 13:16 attrib.xml
-rw-rw-r--   1 mnutter  mnutter   7445892 Sep 22 13:16 child.xml
-rwxr-xr-x   1 mnutter  mnutter       976 Sep 22 13:16 make.pl
$ gzip attrib.xml
$ gzip child.xml
$ ls -l
total 1127
-rw-rw-r--   1 mnutter  mnutter    671039 Sep 22 13:16 attrib.xml.gz
-rw-rw-r--   1 mnutter  mnutter    472394 Sep 22 13:16 child.xml.gz
-rwxr-xr-x   1 mnutter  mnutter       976 Sep 22 13:16 make.pl

I used gzip as an example of off-the-shelf compression technology.  As you can see, even though the raw child.xml file is larger, the compressed version is *smaller* than the corresponding implementation with attributes.

This may not be true in all cases, of course, but I expect it often will, due to the way such compression algorithms work.

For your reference, here is the Perl script I used to create the two files:

open WORDS, "</usr/dict/words" or die "Couldn't open dictionary.\n";
open ATTRIB, ">attrib.xml" or die "Couldn't open attrib.xml\n";
open CHILD, ">child.xml" or die "Couldn't open child.xml\n";

@twenty_strings = qw(one two three four five six seven eight nine ten
                     eleven twelve thirteen fourteen fifteen sixteen
                     seventeen eighteen nineteen twenty);

print ATTRIB "<attrib>\n";
print CHILD "<child>\n";

while($word = <WORDS>)
{
    $time = time();
    $timestr = localtime($time);
    $twenty = rand % 20;
    $twentystr = $twenty_strings[$twenty];
    print ATTRIB <<EOM;
  <word time="$time" timestr="$timestr" twenty="$twenty"
        twentystr="$twentystr">$word</word>
EOM
    print CHILD <<EOM;
  <word>
    <time>$time</time>
    <timestr>$timestr</timestr>
    <twenty>$twenty</twenty>
    <twentystr>$twentystr</twentystr>
  </word>
EOM
}

print ATTRIB "</attrib>\n";
print CHILD "</child>\n";

close CHILD;
close ATTRIB;
close WORDS;

-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-

Mark Nutter, <mnutter@fore.com>

Internet Applications Developer

FORE Systems

Some people are atheists 'til the day they die.