Paul Everitt and I have long been communicating about the role of XML in the CMS world. Recently, he posted the following blog entry and asked for my opinions per email. I started writing a mail back to him, but then I realized I have a blog now too...
Firstly, I want the UdellCMS too. :) Infrae has been trying to build one for a while, staggering along the way.
Now as to some comments to Paul's vision. Within Infrae I have the reputation of being a devil's advocates, and I've done it to Paul before, so here goes with my comments.
Paul mentions, referring to the demo he links to, that:
it isn't a "programming language" (though it sure looks like one)
This one is never going to fly. It's a programming language all right, though a highly declarative one. It's going to take someone with programming skills to write these. The advantage, similar to SQL, is reporting: you do not need to know a lot of APIs in order to extract data out of the system.
Now to what Paul and I both agree is the more interesting bit:
What's more interesting, IMO, is the effect this has on CMS design. It totally changes your approach to navigation. Instead of thinking very hard about folder structures or topic structures, you just throw everything into a big pile and let stored semi-structured and full-text queries create smaller piles. This allows numerous approaches to site navigation.
I think that this approach opens more possibilities than some traditional CMS approaches have been taken, because of its non-API oriented query/reporting nature. This also ties in to various content repository projects, such as Infrae's Railroad and content repository APIs like JSR-170.
But, I also think that you cannot just give up (up-front) thinking about things like folder structures or topic structures, or structured document content, for a number of reasons.
While the files in the referenced demo are perhaps in one big pile, these files contain a lot of structure that can be exploited. It's just not represented as folders and topics. Someone has to put this structure in there.
How will you get (non-computer-savvy) people to produce such structured content? I.e. how do you get enough consistency to actually be able to do smart queries like the ones demonstrated? Jon Udell alone can be trusted to produce semantic XHTML, but a whole organization? With Silva, we took a lot of care so that we get some semi-structured content out of it all (Silva XML).
In addition, organizations use structuring techniques like folders and (mandatory) metadata to have something to hold on to and some coherence in the produced content. You can use folders for authorization, for instance. You also need some uniformity in the topics used by people, and often organizations want to mandate this.
So, some structuring facility seems unavoidable in a CMS. Wikipedia has shown that even minimal facilities can lead to grand things, though, but wikis aren't right for all use cases.
Where the real merit lies is in giving up some APIs and going more to declarative data. In one way that's just moving the problem. But in another way, what you can gain is that you can move some CMS-style tasks away from a potentially limiting set of APIs to a more powerful query & reporting model. In order words, you manufactor serendipity; you make it easier to reuse content in new ways. It all being done in a standardized way (the host of XML standards) is cool of course.
We've been doing things like this at Infrae and with Silva for quite a while now, and we're trying to open it up more. It's not easy and the benefits are sometimes hard to see, but we're trying. But we can extract PDFs and Word documents from Silva, and with custom apps on top of Silva we can expose and relate data in a lot of interesting ways. When you start turning it into a real applicat And we'd like to do more in the future, as we're opening up Silva to accept more kinds of XML content.