Does the World Need Binary XML?

sebFlyte writes "One of XML's founders says 'If I were world dictator, I'd put a kibosh on binary XML' in this interesting look at what can be done to make XML better, faster and stronger."

Comments

Binary XML has been around a while...

[PipianJ]

Binary XML is nothing new, as I wager that many people here are already using it, albeit unknowingly.

One of the earliest projects that has tried to make a binary XML (as far as I'm aware) was the EBML (Extensible Binary Meta-Language) which is used in the Matroska media container.

Re:KISS

[Ramses0]

On the surface that works, but it only solves a portion of the problem.

Data => XML.

XML == large (lots of verbose tags)

XML == slow (have to parse it all [dom], or
build big stacks [sax] to get at data)

Solution:

XML => .xml.gz

You've solved (kindof) the large problem, but you still keep the slow problem.

What they're suggesting is nothing more than:

XML => .xml.gzxml

Basically using a specialized compression schemes that understand the ordered structure of XML, tags, etc, and probably has some indexes to say "here's the locations of all the [blah] tags", attributes so you can just fseek() instead of having to do domwalking or stack-building. This is important for XML selectors (XQuery), and for "big iron" junk, it makes a lot of sense and can save a lot of processing power. Consider that Zip/Tar already do something similar by providing a file-list header as part of their specifications (wouldn't it suck to have completely to unzip a zip file when all you wanted was to be able to pull out a list of the filenames / sizes?)

"Consumer"/Desktop applications already do compress XML (look at star-office as a great example, even JAR is just zipped up stuff which can include XML configs, etc). It's the stream-based data processors that really benefit from a standardized binary-transmission format for XML with some convenient indexes built in.

That is all.

--Robert

XML doesn't need to be non-ascii to be small

[iabervon]

Three ideas, in order of increasing significance and increasing difficulty:

Stop using bad DTDs. There seems to be a DTD style in which you avoid using attributes and instead add a whole lot of tags containing text. Any element with a content type of CDATA should be an attribute on its parent, which improves the readability of documents and lets you use ID/IDREF to automatically check stuff. Once you get rid of the complete cruft, it's not nearly so bad.

Now that everything other than HTML is generally valid XML, it's possible to get rid of a lot of the verbosity of XML, too. A new XML could make all close tags "</", since the name of the element you're closing is predetermined and there's nothing permitted after a slash other than a >. The > could be dropped from empty tags, too. If you know that your DTD will be available and not change during the life of the document, you could use numeric references in open tags to refer to the indexed child element type of the type of the element you're in, and numeric references for the indexed attribute of the element it's on. If you then drop the spaces after close quotes, you've basically removed all of the superfluous size of XML without using a binary format, as well as making string comparisons unnecessary in the parser.

Of course, you could document it as if it were binary. An open tag is indicated with an 0x3C, followed by the index of the element type plus 0x30 (for indices under 0xA). A close tag is (big-endian) 0x3C2F. A non-close tag is an open tag if it ends with an 0x3E and an empty tag if it ends with an 0x2F. Attribute indices are followed with an 0x3D. And so forth.