chimpability

JRuby – Understanding the fuss

Some background, Ruby is a dynamically typed, pure OO language. It’s open source, pretty easy to write and fairly powerful. A couple of deficiencies being addressed in the current 2.0 effort include green threads and unicode support.

Everything in Ruby is an object, dynamically typed, though strongly typed. However, type is less important than behaviour:

Duck typing, runtime exceptions (sounds scary, but rarely happen – I’m waiting to be convinced!).
Mixin modules allow you to include additional behaviour e.g. class Circle include ShapeStuff.

Blocks are nameless functions you can pass and invoke to remove repetitive code.

Well, that’s my version of Ruby in a very small nutshell, now onto JRuby – a Java implementation oof Ruby.

JRuby, gives you easy integration with Java libraries, and you can call to Ruby from Java via JSR-223, and use Java classes from Ruby.

include Java
import javax.swing.JFrame

Now you can script Java.

JRuby offers a rapid MVC framework, and prefers convention over configuration.

So why do Java users want it?

- easy to learn
- less code
- features missing from Java (closures, open classes, literals for Arrays and duck typing)

It’s a better language for tying libraries together, and you can easily create domain specific languages (DSLs)to wrap libraries.

There’s also JRuby on Rails for Java developers, much less rails code than Java application config, and simple CRUD apps in minutes.

Am I sold? Not yet…then again I am biased. There’s more on DSL’s latter this week.

No T-shirt hurling machines this year, which is a shame.

Three main themes as teasers, Netbeans, Semantic Web and SPOT.

Firstly, from the community itself, there’s now a PDF Netbeans magazine on the community website, looks good, useful articles, and the right price

Then we had Henry Story and Tim Boudreau, on making the semantic web dog simple (there’s a dog theme here, we’ll get to it soon).

Quick Recap:
URI – Identifies a resource e.g. documents, people,concepts

REST – REpresentational State Transfer. Things to remember, a resource can return any number of representations, representation can be cached on the Internet, and REST describes the architectural style of the web.

Consider a database table, at the intersection of a row and column, there is a value with a name. In this instance the relationship is local not universal, therefore we need to turn all these relations into URI’s like relation, subject, object (aka triples).

One of the added benefits here is that because we use URI’s, we can click on them to follow the object, and what that is giving us is self describing metadata about objects.

With it so far? Well, that’s the basics, and coincidently these, subject, relation/property, objects are how RDF, the Resource Description Framework classifies things.

And these are at the heart of the Semantic Web. The semantic web, requires structured data, and people don’t like creating structure, but many of the tools we already use create structures

- blog engines like MovableType
- Social networking sites (FOAF)
- Open Source project sites

At the heart of it, is a simple scheme, based on URIs, delivered on a scalable simple mechanism (REST), using RDF which can’t have any less than a subject-relation-object, and it’s clickable.

They gave an example of a scheme for describing projects (project, homepage, license etc.) DOAP (description of a project).

Finally, Bob Beasly showing off a rich client app he’d built, and he’s a non-techie, using the visual web pack. Well, I thought I’d seen it all….No, he’s built a webapp he can use to remotely control a PC that he uses to train his dog. He clicks buttons to re-play WAV files to command the dog to sit etc. then click another button to reward the dog ‘Sadie’.All watched via webcam. Well the reward mechanism uses a SunSpot device (see http://www.sunspotworld.com), to activate a chute that delivers a doggie treat.

Good to see the most expensive dog feeder on the planet.