Original URL: http://www.theregister.co.uk/2011/03/11/w3c_exi/

W3C squeezes XML into portability

Is that a schema in your pocket...

By Bill Ray

Posted in Mobile, 11th March 2011 10:35 GMT

Web-standards group the W3C has published its preferred standard for compressing XML documents into something more suitable for transmission over radio, and perhaps everywhere else too.

Efficient XML Interchange (EXI) originated with a company called AgileDelta, whose CTO is still editor of the specification which tokenises XML tags to create a significantly smaller binary file. That's easier for a computer to interpret as well as being quicker to transmit, which should lead to wider adoption of XML in embedded devices and let EXI supplant XML entirely in some applications.

Which would be no bad thing for the machines: XML is good at being human readable, and interoperable, but is horribly inefficient. XML documents contain huge amounts of replication and redundancy which we humans seem to enjoy, but it clogs up computers terribly and can be cut out with no loss of functionality.

There are already various ways of compressing XML documents: they can be zipped up for transmission, or use one of the various competing conversions that claim their own efficiencies. EXI can make use of the XML document's schema to create its compressed version, which makes encoding a little more complicated but simplifies decoding and increases the compression (so, for example, tags that only occur nested within different parents can share the same name).

With the W3C's blessing, EXI will be the standard with which to be seen, and there are already half a dozen open source and commercial implementations to play with, as long as you no longer need documents readable by our inefficient human brains. ®