[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: XML / HTML Transport size
Danny Ayers writes: > fyi: Scalable Vector Graphics (SVG) [1] allows for the use of the > familiar gzip compression scheme, achieving worthwhile ratios. The > Adobe SVG browser plugin supports this, and all in all it seems a > successful approach. zlib makes it trivially easy to support something like that cross-platform -- we make extensive use of it in FlightGear (Linux/FreeBSD/Windows/Irix/Solaris/MacOS/etc. etc.) for non-binary input files. If the input data is very, very randomized, then binary input formats tend to be smaller than compressed XML, but not by as much as you might expect. Consider a file containing 10,000 pairs of pseudo-random integers. In a binary format using 4 bytes for each integer, the file would require 80,000 bytes. I generated the pairs in an XML format like this: <value> <component-a>448773211</component-a> <component-b>539257706</component-b> </value> As you might expect, the resulting XML file was very large (13 times the size of the binary file): -rw-r--r-- 1 david david 1039309 Nov 18 12:46 foo.xml Given that the integers are psuedo-random, and thus, lacking in repetitive patterns, you wouldn't expect compressors to do a good job -- they can factor out the tags, but not the numbers. However, plain old gzip (-9) did pretty well, all considered: -rw-r--r-- 1 david david 127976 Nov 18 12:46 foo.xml.gz That's only 1.6 times the size of the binary file. Of course, bzip (-9) did even better: -rw-r--r-- 1 david david 91608 Nov 18 12:46 foo.xml.bz2 That's down to 1.2 times the size of the binary file. So, the worst case isn't that bad, and in most real-life cases I've seen, where the data has a lot more repetition, the compressed text wins. All the best, David -- David Megginson, david@m..., http://www.megginson.com/
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