XML Love In

Ok, so realize that to some people XML is just a bit overrated and not worth getting excited about. I know, I used to be one. Sure there's some benefit in having a standardized syntax but when I first learn about XML I couldn't see beyond that. It was just a way of adding a standard structure to your file yet to me that structure was still arbitrary.

Fast foward to the present and I'm starting to realize that the real benefit of XML is having lots of standards use it. When my web pages, my images and my data are all in XML I can begin to do some powerful things like covert my data into an image automatically (XML -> SVG via XSLT). I can also do powerful things like create a form that automatically binds to the XML data I give it without me having to carefully construct it. XForms (though support is currently weak) will be a huge improvement over the current HTML forms as you can throw many inputs into your form and only the ones that match your XML data will be used! Great concept.

So yes, I've gotten the XML bug just a little though it's not all straight sailing. Despite knowing that I can convert my XML data into images I still haven't managed to get it working as I expect it should. Browsers are still weak on allowing you to debug XSLT. Sure I could generate the SVG server side, still using XSLT if I wished but that's not the point. I want to deliver the data to the browser and let it render it as needed.

I've got the bug so bad that Im' now thinking of all the ways I can use XML in my intranet site. I want to experiment with submitting XForms via SOAP (though I thnk thats XForms 1.1) and I want to look at being able to pull an XForms instance via SOAP also. I would like to be able to use XSLT to completely transform my data into a web page that looks the same as my existing pages. Then all I would need to worry about was the correct generation of my XML data. I would also like to better validate my data against my still growing schema. I would like to be able to use XSLT to transform my XML data into formats for use by other applications.

So many things to think about. The power of XML is just begining to dawn on me and I'm enjoying it. Just though I would share all this with you nice folks.

If anyone out there has managed to get embedded SVG (ie in an XHTML page) working form an XSLT tranformation of XML data withing firefox then I'd love to hear about it.

Thanks.

Magical Mystical iPhone

I must be an old school shopper but I don't like walking into a store and buying something that doesn't require delivery yet not walking out with the product.

Yet every Optus store I walk into (yes I know other people have stock) tells me it's going to be 6-8 weeks to get them in and that's only if I sign up now!

I don't know about you but I don't like the idea of paying for an iPhone plan (more $$ than my current plan) without actually having an iPhone. Is Optus going to reimburse me? I don't think so.

So instead I am waiting until I can walk into a store sign up and walk out with an iPhone. I don't think that's unreasonable. Given that, one can hardly say that the iPhone is generally available. I mean if you can't walk into a store and get one how is that available? If every store has to effectively 'order in' you iPhone that's not really available is it?

Really the iPhone has had a limited release. Even the Optus resellers don't have any iPhones and won't for some time so it would appear.

Apple should have gauaged the demand better and had sufficient stocks on hand. You don't made a really cool device that everyone wants then limit stocks for months after release. How does that help anyone. Surely there are loosing sales to people who unlike me can't be bothered waiting.

Heavens knows.

So still I wait.

Crowd Sourcing the Semantic Web

I've always been interested in the potential power of the semantic web but until now there hasn't appeared to be any killer application. I mean sure there's semantic information out there but most of it is what I would consider high brow. Databases of scientific information converted to semantic web form.

Yet what I always thought was the most obvious use of the semantic web technology would be to build a repository of human knowledge.

Ok, first you think wikipedia then if you're savvy you think of all the efforts out there to turn things like wikipedia into semantic information.

What I am thinking is something much more. I am imagining a website, or even a series of websites where people could input semantic information. I guess a semantic version of wikipedia though I can't think of a cool name.

People would go to this website with the intent of creating semantic knowledge. For instance you could go there and input the information that table is flat and has legs and that an average table will have four legs. The idea is not that I now become the authoratative source on tables but that I have just input a tiny piece if information.

From there we apply the crowd sourcing principle and probability networks to weigh each piece of information that the crowd has entered. If enough people input information about a table that is similar, that information becomes a fact. I believe this is the closest approximation to how we as humans learn.

The biggest failing of wikipedia is that even though I can input fantastic information the next person can overide that information. I would prefer that the next person input their information under the same heading and the system work out what most people believe based on the most popular information.

There are reasoning systems out there that can work on information like this. This would allow anyone to input any information (like wikipedia) but rather than anyone being able to overright any information you would have to fight against the crowd. So if 50,000 people put in information about a table being flat with legs and 6 people said that they were round and squishy a reasoning system would still come to the right conclusion.

So that's my great idea. Perhaps it's already being done but I don't know of it. I think if we were to stay standards compliant then we would have to have some way of crowd sourcing the ontology that goes with everything. I think there is potential here.

Then people could point their probability reasoners at this store of knowledge and could actually begin to understand human knowledge.

Google are you listening?

XSLT

After spending so much time generating my XML data I decided that I wanted to be able to see it presented in a user friendly fashion. Enter XML Stylesheets.

Boy what a frustrating time I had getting these to work. I found two big problems that took some time to solve.

The first problem that I had was originally the browser complained about my stylesheet because the web server reported its mimetype as text/xml and suggested it should be text/css. I reconfigured the webserver thinking this was the problem (of no output) but found that the browser then tried to interpret my XML stylesheet as CSS and produces a multitude of errors as a result.

So after changing it back (and still not working) I finally hit upon the solution. The web server has to report the file as text/xml but the source XML file has to tell the browser that it is text/xsl so the browser knows how to interpret it.

Secondly, I found that although I wrote a valid stylesheet for reasons that I couldn't fathom it produced either no output or wrong output. The browser will only complain at you when your stylesheet is not valid or well formed but if it passes these two tests there is no way to ask it what is wrong with the stylesheet.

So then I had to start with the most basic stylesheet and work my way up from there. One of the things that caught me out was the matching system. If for some reason your templates didn't match everything in the XML file the the browser would just dump any XML that was left over. This was a huge source of frustration as I had the impression that anything not matched would be ignored.

I did finally get a reasonablly working stylesheet:

https://netdb.alphawest.com.au/xml/netdb-style.xsl

Now it is a simply task as I add a new node to the XML output to create a new template into the stylesheet and get it parsed as the appropriate place. Simple now that it works!

XML and Schemas

I have embarked upon a project to output XML data from my intranet application. For what end I don't know yet but I thought it would be a useful exercise to have the ability to have my data in XML format.

My first attempt was the usual ad hoc method of simply outputting some XML but as I progressed I realized that I had no clear picture of what the XML should look like.

So this time around I have started with the other end and begun developing an XML schema.

https://netdb.alphawest.com.au/xml/netdb.xsd

I have done this with the assistance of Eclipse which has a nice GUI based tool for generating XML Schema. I now understand how it all hangs together and thus now have a nicely structured schema file describing what the XML form of my data should look like.

It has now become a much easier task to write the PHP code to output XML that complies with the schema. I have yet worked out a method to validate my generated XML against the schema without paying for software. Perhaps someone can recommend something.

My lesson learned from this experience is it pays to design your data first.

The next challenge is to find a useful application of this XML data. I would love to do some semantic web stuff with it but it tends to require RDF formatted data which would throw out the schema and probably require instead an OWL file describing what triples can exist.

I'll keep you posted on that.

The wonderful world of XSD

I have decided that for reasons that I don't yet understand, I am delving into the world of XML Schemas. From starting out thinking it's a relatively easy thing to describe your data to realizing what a huge task it is, I am now getting the hang of this and hopefully will be able to move on up to OWL once I am done here.

Understanding you data is the first task in creating a good schema definition. I have a standard relational database where I store all the information for my intranet web application. Sounds simply so far. Things start to get complicated when I mention that the database is actually an object relational one and yes I have tables that are inherited from other tables. Then most of these tables are represented at the middleware level by a bunch of PHP classes all inherited from a single parent.

With me so far? So from all that I want to create a schema that describes all the data that I have. Except that not all the data exists in the database and the data fakes some heirarchical information that has to now be represented in XML.

So, as you can guess, I'm having fun so far. I have an idea of the size of the task now and realize that I must spend some time making the right choices so that I end up with a useful and complete model of my data.

Wish me luck.

Apache SSL on Solaris

Ok, this is not a how to but a caveat. I downloaded Apache 2.2.8 onto my Solaris 9 box with the intention of upgrading from 2.0.47 and also enabling SSL. The upgrade part went fine after I managed to work out that to enable mod_ssl you need to provide two options to ./configure those being:

$ ./configure --enable-ssl --with-ssl=/usr/local/ssl

Or wherever your ssl is located. That took me a while as previously there was just the one option.

Secondly, (and this was a hard one) after installing the new apache I could not get SSL to work. On startup apache logged that it had loaded mod_ssl and generated some keys but it would not listen on port 443. I had a clue when I removed the Listen 80 statement for normal web traffic. This made apache complain that there were no ports to listen on. Ahh, it was ignoring my ssl config (contained in ssl.conf). That config was encased in a tag which it turns out was invalid (perhaps hangover from previous ssl config). Commenting it out (and the closing tag) made everything work after fixing a few more errrors.

So I guess the lesson to be learned here is that we shouldn't trust the config from the previous version of software. Too many assumptions are being made. I also don't understand why the ssl.conf file was conditionally included depending on the presense of the mod_ssl module yet the ssl.conf file had another conditional (which turned out to be broken). Why the double checking?

Oh well, at least it works now.

Feels good to be on the blu side

In case you haven't heard, HD-DVD is dead. Toshiba have officially pulled the plug. Some may want to cling onto their players but without any new content it will be a lonely ride.

Having just gotten a PS3 (for the games) it feels good to be on the winning side either way. From the beginning I was hoping that blu-ray would win, it just seemed like the better thought out design.

Either way, the deed is done and we can all look forward to every dvd we know being rereleased on blu-ray. Yay.