I Think, Therefore I eXist ...

by Kurt Cagle

I've been thinking about the Kudzu principle a lot lately. This particular "rule" was something I first observed in about 1999, and it goes something like this - XML, once introduced into a system, will over time continue to expand into that system. Kudzu was originally introduced into the American Southeast in the 1800s, in order to provide a way to more readily secure the loose clay soil that's so predominant there. Unfortunately, like many invasive plants it very quickly expanded beyond its original boundaries and became one of the most aggressive weeds in the region.

XML is a mechanism for abstraction. Unlike OOP typed objects, however, the abstraction does not place specific requirements upon the local mechanism for implementation - instead XML forms a document object model where each particular element represents what in other languages would be considered classes or class properties (either implicitly declared - i.e., a string object, or explicitly declared). Because of this, it becomes possible to manipulate that particular object model using a generic set of commands that in general are unaware of the underlying semantics of the given class or property.


M. David Peterson
2006-09-18 04:10:45
Glad to see you've spent the time to play with eXist, Kurt... There are a few others that kinda/sorta fill the XQuery/XSLT Application space, but the only one with any real credibility (as an application server. Plenty of XQuery DB's that are really quite nice) is SQL Server 2005/Express which fills things nicely from an XQuery/XSLT 1.0 space, and its FAST AS... + you can code in any other language supported on the .NET platform.

The downside to SS2005/E is thats its not cross-platform and not open-source, though the OSS side of things is not something I see as a problem... I can build and extend from it all I want, which fills my needs just fine.

Bob DuCharme
2006-09-18 05:54:41
Hi Kurt,

"a re-design of eXist's indexing engine paid for itself quite handsomely" Was that in the transition from 1.0 to 1.1? I found 1.0 to be a bit slow, and was encouraged by what I saw at http://exist.sourceforge.net/index.html#download.

People interested in starting with eXist from scratch may find this article useful.

2006-09-18 06:00:33



Three of a number of hits in order of idea emergence.

Credit isn't just about 'showing up', as Tim says. It is about
checking sources. This is why PageRanking works and why it doesn't.

Sustainability trumps authority.

Kurt Cagle
2006-09-18 11:22:56

The transition was 1.0 to 1.1 - I agree with you that 1.0 seemed slow to me, and the indexing rework has definitely been worth it. I'll edit that to make it clearer.

-- Kurt

Kurt Cagle
2006-09-18 11:30:44

I've played a fair amount with SQL Server Express, but in this particular case the cross platform aspect was a major part of the requirements, both from a dev and a deployment standpoint. The customer is running a Linux server, having been burned more than once by bad Windows developers - not necessarily a fault of the OS, of course, but it makes it harder to propose a solution in that space when the last project the CEO did on Windows went belly-up.

Microsoft applications need to get out of this rut of supporting only the Windows OS. I suspect that SQL Server for Linux would actually prove to be quite profitable for them, giving them a solid heterogenous base by which to embrace and extend into the Linux space itself.

-- Kurt

Kurt Cagle
2006-09-18 11:35:10

BTW, thanks for the article you wrote earlier - when I was evaluating XQuery databases, it was definitely the best article I found on the topic, and proved instrumental in helping me decide to go with eXist as my database of choice for a client.

-- Kurt

Kurt Cagle
2006-09-18 11:49:15

I suspect only those of us who have spent serious time in the south (I lived in Montgomery for four years as a kid) really understand the kudzu metaphor - we had a hill in the back of our house where the developers had put down kudzu in order to stabilize the red clay soil from eroding in the frequent thunderstorms, and I remember at age ten hacking away at it (and the rhubarb that was infesting our garden, yet another opportunistic import) trying to keep it from taking over the garden at the base of the hill.

The funny thing about the "XML as kudzu" argument is that I find it only gains more relevance over time. We need the structure that XML imposes, so long as that structure does not become so restrictive as to be constraining. I liken it to the order/chaos balance that LE Modessit has explored to great depth in his Recluse books - you need the order that XML provides in order to generate stability amidst the quickfire of languages such as JavaScript, but stability by itself is only sterility. On the other hand, using XML inappropriately is likely to result in headaches and blindness ... hmmm, not going there..

-- Kurt

2006-09-18 19:17:41
Tim Bray posts an article today about the authority of WikiPedia references. Some of us have been worrying for a long time about search system ranking. At the same time there are discussions of using published ideas for patent validation. Early hypertext pioneers worried about citations and their effect on the authority of crediting ideas. Xanadu and other attempts become as complex as they do in part trying to satisfy this requirement.

Simple searches reveal timeliness if not quotation lineage. Berners-Lee talked about independent invention as being a primary quality of the worthiness of the idea. Copyright is not about the ability of the government to defend the right, but is about using the government as a witness. The holder has to defend the right.

The Kudzu is both exemplar and metaphor for the tangled weave of ideas illustrating the single problem of 'who says it first'. In a world of assertion of reputation and reputation management, we either give up the right or we begin to develop even more complex technologies to defend it.

Who invented XML? No one? Every one? I can point to the citations but are they right or just the artifact of who was the most popular person at the time?

This is tangential to what your article is about, yet your article uses the idea and while we share, who's is it? No one's really, but an interesting example of an elephant in the room of web publishing because as I point out repeatedly here and elsewhere, the Long Tail is inverting and that makes me wonder about the future of the ad-sponsored sites and search engines. The need to corral and control the sources of resources continues to grow, but the very act of doing it causes those sources to fade in value as long as they use the very system they are supporting.

Like the Kudzu, it kills the soil it was supposed to protect. That makes for a neatly recursive idea. Now which one of us owns it? ;-)

Birmingham eh? How are your lungs? Still red dust occluded?

2006-09-18 19:21:06
Oops. Montgomery. Wow. Now that is occlusion at its worst.

All you suffered was severe boredom. Montgomery is a company town if ever there was one.

Bob DuCharme
2006-09-18 20:33:03
Thanks Kurt. I've added a pointer to this piece at the end of part 1 of that article.
Sylvain Hellegouarch
2006-09-19 03:01:43
Ha Kurt, I felt the same when I first tried eXist a year or so ago. For now I didn't find a time to include in my projects but I think I will try to set it as a backend for my Python implementation of the Atom Pub. Protocol.
2006-09-19 05:32:23
Constraints create structure. Chaos is the engine of evolution.

Targeted selection?

Kudzu spreads the same way pines do: they eliminate opportunities for competitors to thrive. XML is not actually kudzu except at the level of the syntax. HTML is kudzu at the level of weak semantics but all naming systems have some degree of that quality. What you want to know is where on the scale from the pine (toxic to competitors because of what needles do to soil) to kudzu which is not toxic to the soil but proliferate so fast that a competitor only survives proportionally to its strength (think kudzu covered trees vs grass).

Once again, it comes down to the force vector qualities of the object in the environment over the ease with which it can proliferate (eg, HTML isn't the winner because it is the best but because it is easy to remember and therefore author for a tipping point percentage of applications). Then it comes down to awareness or buzz and that is why I come back to the PageRank over Wikipedia effect: sustainability over authority.

If I were Tim I wouldn't worry too much. If over time Wikipedia proves to be poisoned soil, the only thing that will grow there is weeds. It takes time but feedback-based systems either equalize at some optima or they collapse. See PID controllers.

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