Good grief, how did I miss this!! Shane Hathaway wrote:
I just read the RDF article published here:http://www.xml.com/pub/a/2003/02/12/rdflib.html
Yes indeed, that is a very good article.
I've understood the mechanics of RDF for a while, but never understood what makes it better than what we already have. Now I think I get it: RDF theory is a new kind of database abstraction. It's similar to a relational database in that you put pieces of data into the database and later search for data. But it's much more ad-hoc than a relational database.I think you are 100% correct, maybe 110%. :^)
In the last two years I made several attempts at grokking Mozilla and RDF was always the wall I ran into that prevented further progress. In the last three months I slowly, surely, forced myself to study it. Write things down, take notes, rewrite them down, etc.
The light bulb has definitely gone off for me now, and I see things exactly the way you describe it:
1) It's an abstraction. Once you start working with it, you realize what this means. You take a bunch of information and throw it into a bucket. You also throw in how the information relates to each other.
2) It's a database. You have a pretty formal way of asking questions and making sense of the stuff in the bucket. You also have a way to put things in the bucket, and also to rearrange the stuff in the bucket.
3) It's ad-hoc. You don't have to know everything beforehand like SQL. You also don't have to control the containment hierarchy like you do with XML. (Took me a LONG time to realize the significance of the latter point.)
The ad-hoc part is, for me, the key. Relational theory provided the theoretical foundation for modern online transaction processing. But things like content management are a much different problem. (One analyst states that unstructured content is 80% of the information in a business.)
RDF, in my view, is the equivalent of a "set theory", a formal foundation, for content management. Without it, everyone has to build their own "framework" for stitching things together, for connecting the dots.
Serialization of RDF into XML and the relationship between RDF and the Semantic Web are distinct concepts from RDF theory.That's right. I've always been surprised when I threw some RDF/XML into Mozilla, then got a dump of the serialized results. What I put in doesn't look like what I get out. That's because there is an abstract model. The XML can look a couple of different ways, and you still have the same abstract model.
It took me a while, but I learned how to take advantage of this. With Moztop, I'm taking a pretty loose, distributed approach to content managment. I collect RDF from a bunch of different servers, throw it all into one big graph, and use this to draw widgets on the screen.
The ability to make an assertion into a completely different part of the tree is something you can't do in XML.
This ad-hoc data storage made me think of TinyTables. TinyTables is a good Zope product that fills the need for simple tables of data, but it needs attention. What if it got replaced by some Zope product calledI will do everything in the universe to help such a project. How is that? :^)
I know what the practical benefits that RDF can mean for content management. And it isn't esoteric Semantic Gibberish. I'm unable, though, to map it on the server side. However, I'm having luck on the client side:
http://www.zope-europe.org/Members/paul/tmp/moztop-pinstripe.png
"RDFBucket"? An RDFBucket object would let you input data in a variety of ways, including object introspection, forms, and XML with embeddedYes, this is very similar to the client side model in Mozilla. I'm doing things like:
o Assembling a hierarchy
o Making up new hierarchies where none existed before
o Generating property sheets
o Doing conditional display
o Making rich connections between loosely-coupled objects, meaning,
objects that didn't expect to be coupled
o Allowing data from Zope 2 and Zope 3 sites to be
collected, presented, and related in the same interface
Mozilla's template model is interesting to at least investigate. What's interesting about it is the way you can follow relationships in the model to draw things on the screen:
http://www.mozilla.org/docs/xul/xulnotes/template-primer.html
In this very simple example:
http://www.mozilla.org/docs/xul/xulnotes/template-bindings.html
...note the last two resources shown in friends.rdf. Instead of repeating information in every "row", you get the equivalent of a join. Except the result of that join can produce another join. The template builder keeps following relationships. Also, you can join to something on another server.
RDF. It would let you run queries similar to ZCatalog. Maybe it would also generate RDF for embedding metadata in web pagesYou're on track, oh boy, you're on track. :^)
I'm wondering if I'm thinking in line with RDF theory, or if I've veered off track. If you're familiar with RDF: What do you think?
To get this back into the world of the living, it would be helpful to think of a sample application. Here's one we all know very well: Collector/Tracker. Could you write a tracker system in RDFBucket without writing domain-specific objects? (Yup.)
The nature of this kind of application is particularly well suited to your discussion.
Another that is particularly well-suited: a Zope version of Microsoft Project, where you have Tasks, Resources, dependencies, etc.
--Paul
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