Question

Is there any reason why XML such as this :

<person>         <firstname>Joe</firstname>         <lastname>Plumber</lastname> </person> 

couldn’t be compressed like this for client/server transfer.

<person>         <firstname>Joe</>         <lastname>Plumber</> </> 

It would be smaller – and slightly faster to parse.

Assuming that there are no edge conditions meaning this wouldn’t work – are there any libraries to do such a thing?

This is a hard thing to google it turns out :

Your search – </> – did not match any documents.

Suggestions:

Try different keywords.

Edit: Seems to be confusion in what I’m asking. I am talkin about my own form of compression. I am fully aware that as it stands this is NOT XML. The server and client would have to be ‘in on the scheme’. It would be especially helpful for schemas that have very long element names, becuase the bandwidth taken up by those element names would be halved.

Answer 1

That’s not valid XML. Closing tags must be named. It’s potentially error prone otherwise and frankly I think it’d be less readable your way.

In reference to your clarification about this being a nonstandard violation of the XML standard to save a few bytes, it is an incredibly bad idea for several reasons:

1. It’s nonstandard and possibly will have to be supported far in the future;
2. Standards exist for a reason. Standards and conventions have a lot of power and having ‘custom XML’ ranks up there with Ivory Tower graphic designers who force programmers to write a custom button replacement because the standard one can’t do whatever weird, wonderful and confusing behaviour was dreamt up;
3. Gzip compression is easy and far more effective and won’t break standards. If you see a gzip octet stream, there’s no mistaking it for XML. The real problem with the shorthand scheme you’ve got is that it still has at the top so some poor unsuspecting parser may make the mistake of thinking its valid and bomb out with a different, misleading error;
4. Information theory: compression works by removing redundancy of information. If you do that by hand, it makes gzip compression no more effective because the same amount of information is represetned;
5. There is a significant overhead on converting documents to and from this scheme. It can’t be done with a standard XML parser so you’d have to effectively write your own XML parser and outputter that understands this scheme (actually conversion to this format can be done with a parser; getting it back is more difficult), which is a lot of work (and a lot of bugs).