This is the fifth and last installment in my summary of the sessions I attended at JavaOne this year.


The previous installments covered Java futures, Java programming practice, concurrency, and JMX stuff.

Once again, the titles here are not always the ones that appear in the conference programme. I tried to undo the mangling that the Trademark Police typically impose on talk titles, so let me just state up front that Java, JMX, and JVM are trademarks of Sun Microsystems, Inc., and any other abbreviation beginning with J has a sporting chance of being one too.

Here are the sessions summarized in this installment:

The Garbage-First Garbage Collector
Jamming with Java: Making Music with JFugue and JFrets
Semantic Web for the Working Ontologist
General Session: Extreme Innovation (the Toy Show)

TS-5419, The Garbage-First Garbage Collector, Paul Ciciora, Antonios Printezis. Antonios (Tony) presented the "Garbage-First" Garbage Collector, nicknamed G1, which will be showing up in an update of JDK 6. This is an improved version of the CMS collector (also originally designed by Tony). The new collector is better because it does not fragment memory as CMS can, and it does not require tuning the sizes of separate memory areas as CMS does. The performance should also be better. What made this presentation work was the painstakingly-constructed diagrams, which really helped understand the underlying ideas.

Tony talks more about this in an interview on the JavaOne website.

TS-5263, Jamming with Java: Making Music with JFugue and JFrets, David Koelle, Matt Warman. JFugue is a very nifty system that allows you to represent MIDI sequences with strings. This is hugely easier to work with than the javax.sound.midi API. JFugue adds useful notions like repeated patterns, which can be submitted to arbitrary transformers. It supports tapping out rhythms using arbitrary characters and then applying a substitution that says for example that *means a snare drum eighth-note and . means an eighth-note rest, so ..*...*. is a pattern that hits the virtual snare drum on the weak beats in 4/4 time.

Pedant moment. The melody shown for Frère Jacques in the slides had a D instead of a C as the fourth note, which means it wouldn't work as a round.

JFrets builds on JFugue to provide an app that does guitar tablature. I don't have much to do with tablature but JFrets seemed pretty useful for those who do.

TS-5555, Semantic Web for the Working Ontologist, Dean Allemang. I generally try to fit in at least a couple of sessions that are completely unrelated to my professional activities, and this is one. I chose this one because, like many people, I'd heard the term "semantic web" being bandied about but I didn't have any real idea of what it meant. Also, I know Dean from way back.

I think this area suffers from frightening terminology such as "ontologies" and indeed "semantic web" itself. It sounds a lot more complicated than it actually is. Which is not to say that it is simple.

The basic idea as I understand it is that today we have this fantastic web of human-readable information. We'd like to build on that infrastructure to create a web of machine-readable information as well.

Some questions are rather easy for people to answer by browsing the web. For example: who were the speakers at JavaOne 2008? But programs can't easily answer such questions because the human-readable information on the web isn't formally structured. The Semantic Web would allow web pages to be structured in a way that allows a program to understand them, without needing to build logic into the program for each information set.

There's an obvious parallel here with web forms intended to be filled out by humans, versus web services APIs intended to be called by programs. I don't know enough about the area to be able to say whether this might mean there is a sort of rivalry between web services and the semantic web.

I found it possible not to be scared by the word "ontology" by mentally replacing it with "schema". An "ontology" represents a set of concepts and the relationships between them. Well if that isn't a schema, it's near enough to one for me.

One thing Dean stressed is that it isn't necessary for some standards body to create all the world's schemas. The semantic web includes support for mapping between the concepts of different schemas, for example to say that "address" in my schema is the same as "location" in your schema. Of course there could be subtle differences in the semantics (perhaps "location" can represent the North Pole while "address" can't), but you can still get a lot of useful work done even with these mismatches at the edges.

And that's enough about the Semantic Web to be able to avoid sounding stupid when talking about it at parties. This talk, and the fact of writing it up, has led me to discover some promising starting points for further exploration, of which the best I've found is an article called Giant Global Graph by Tim Berners-Lee.

Sun General Session, Extreme Innovation, James Gosling and guests. Also known as the Toy Show, this is the annual overdose of geekery where James shows all the latest nifty stuff. It also doubles as a good way for the conference organizers to persuade people to stay around for the last day of the conference.

Unusually, I was right there at 8:30am when the show was due to start, because I knew that the first item would be VisualVM, being demonstrated by Tomas Hurkaand my teammate Luis-Miguel Alventosa. Equal measures of pride and stress for them, I think, as they stood up and demoed their stuff in front of thousands of people in a huge dark auditorium. In the event, the demo went off perfectly, as did the other demos from this session. (Unlike the first general session of the conference, but the less said the better.)

If you use JConsole, you should check out VisualVM.

Among the many other nifty things in this session, I liked the contraption that Greg Bollella built to show off Real-Time Java.

Little coloured balls circulate through the plastic tubes, occasionally encountering pinball flippers or a bean machine. Eventually each ball falls past a colour detector and into a sorter. The Real-Time Java system has to flick the right switches while the ball is in free-fall so that it ends up in the right bin. Plain Java wouldn't be up to the job (what if a garbage collection happened at just the wrong time?), but Real-Time Java is. The box at the bottom of the picture is Project "Blue Wonder", a collection of Sun technologies suitable for use in industrial control processes. You can see more details in the video of this part of the session.

But the thing that impressed me most, along with most of the people I was talking to, was the Livescribe smartpen. It records your pen movements as you write and can upload them to a computer to reproduce what you wrote. It records ambient sound at the same time and can upload that as well. If you go back to something you wrote and touch it with the pen, the pen can play back the sound from the time you were writing. You can also search through your writing on the computer (handwriting-recognition algorithms seem to have improved without bound since the last time I was paying attention) and play back there the sound from what you find. There were some other nice demos: drawing a toy piano keyboard, then having the pen sound the notes from the keys you touch; or touching a word with the pen and having it pronounce the equivalent word in Arabic. But even without these I thought the pen would be invaluable to anyone who has to take notes often, for example students. It's not even very expensive: $149.

Jeff bought one for his wife (one can't buy such trivia for oneself of course) and she's apparently very happy with it. The pen needs special paper, but I noted with approval that Livescribe will be making software available so that you can print it yourself if you have a good-quality printer.

Well that's it from me about JavaOne for this year. Back to more mundane blogging...

[Tags: javaone javaone2008 garbage_collection garbage_first jfugue jfrets semantic_web visualvm real_time_java rtsj livescribe smartpen.]