Eduardo Pelegri-Llopart's Blog

March 2005 Archives

Want to help create JAX-WSA?

Arun sent me the following:

JSR 261, Java APIs for XML-based Web Services Addressing, is starting it's work this week. It will define a framework for supporting transport-neutral addressing of Web services based on the specification from W3C WS-Addressing WG. The group is well represented by the major Web services players but we are still accepting additional applications, specially from smaller companies or expert individuals. If you are interested in helping to define this framework and would like to contribute, please consider applying to join.

How to use quotes in comments to blogs

The Software that does previews for blog comments will break your comment if you use a single quote. The solution is to instead use the alternate representations for that character, like:

   The single quote or apostrophe (')  	apos  	'
   The double quote (") 	quot 	"

This means that to say "It's cumbersome", you would actually type

   It's cumbersome

  It's cumbersome

The Javadocs are coming - and that's good!

One of the things that made Java popular is javadocs: a relatively simple way to combine documentation about the code in the code, together with a tool that generates web pages from there. Ideas like this had been around for a while - I tend to think of them as being under the literate programming umbrella, but I'm no expert in the field - but javadocs simplicity and generation of HTML pages was very succesful.

Javadocs are part of the specifications. In some cases the specs are written so they refer to the javadocs; in some other cases the specs include the javadocs directly. The latter was the approach we took with the JSP specs, where we directly generate the (framemaker) API chapters from the javadoc comments in the API files.

Because the javadocs are part of the spec, they are developed by the EG through the same JCP process as the specs. Which is why it is so important that we are seing more cases where the Expert Groups are deciding to release the javadocs in an ongoing manner, to keep the developer community informed of the evolution of the spec, and to encourage them to provide feedback.

This last week has seen two important javadocs released. The first are the javadocs for Mustang; the next version of J2SE. The javadocs can be browsed online and are companions to the binary snapshots and the source snapshots (I notice that the binary and source URLs have a "jdk6" in their URL; I think the javadoc should have one too).

The other set of javadocs are those for JAXB 2.0. Like for Mustang, we have the javadocs and a regular drops that include the javadocs, binaries and sources. We expect the JAX-RPC 2.0 project to do the same in the near future; a version of the binary was included in the technology release for the combined JAXB 2.0 and JAX-RPC 2.0 but the regular, ongoing drops for that technology have not yet started.

We are doing our part: we are going to be releasing to you regular drops of the implementations and the specs. We need you to download these, use them, and give us your feedback through the different feedback forums. For the case of JAXB 2.0 and JAX-RPC 2.0, use this forum. Mustang is asking for feedback through two forums; one for the snapshots, the other for Mustang itself.

Mailing List or Web Forum? - Have Both!

Web-based forums have many appealing properties, but many communities started before web-based forums became popular and had their own, very active, mailing list. Even for new communities, some people like to get all their content by email. Fortunately, some software products bridge between the two worlds, and that is the case for the version of Jive that Java.Net uses. The Jive mechanism is called a "watch".

To set a watch the first thing you need is to login; the software needs to know who you are so it will record your watches! You can then watch specific threads in a Thread or a whole Forum. If you are watching a thread, you will be sent mail notifications when anybody else - not you - posts to that thread. Watching a forum is like watching all threads, exsting or future. For instance, I have a watch on the Binary WS & XML and the JAXB 2.0 and JAX-RPC 2.0 forums.

Java.Net also supports the opposite: all mailing lists can be archived, with a web interface. For example, the archive for the USERS mailing list of the JAXB project.

So, which to use? A mailing list with a web archive, or a forum with a mail watch interface. At some level I think it is a bit arbitrary and contextual, but the guideline I've used with the forums and lists above is that for the Forums are focused on longer-term issues (like specification feedback), and they are less centered around a specific implementation artifact (like the JAXB RI)

Moore's Law and Binary XML

One of the arguments against the need for a binary encoding of XML (like Fast Infoset) can be summed up as: "just wait until the technology catches up", or maybe "Moore's Law makes Binary XML unncessary".

Although that may be true in what some people could describe as "traditional" applications of XML, there are many legitimate use case of XML where this is not so. Many of these use cases have appeared as the market wants to take advantage of the benefits of XML in new fields. There are a number of reasons, some economical in nature, some technological, underlying these use cases.

One basic reason is related to the characteristics of servers servicing many requests:

• Any reduction on the number of servers needed to service a given number of client requests translates into profit.

A related reason is:

• Any time-to-market advantage (not waiting for the technology to catch up) translates into profit.

Here are some reasons related to properties of transmissions:

• Bandwidth may be a limiting factor. For instance, the spectrum is limited and you just can't cram more in there. If you can are more efficient you can save spectrum you can either use less spectrum or generate more content, and be more profitable.
• In some cases there are constraints on time and bandwidth. An inefficient encoding may render an implementation approach invalid.
• Too many wireless packets will produce collisions, which then generate more retransmissions, which then generate even more packets. Thus efficiency in the transmission is critical.

And here is another related to small portable devices:

• Battery life is not following Moore's rule. I've heard discussions of a "packet budget" based on how many packets the device can send given the battery capacity and the desired on-time for the device. Being more efficient can be the difference between a successful product and a failure.

The XML Binary Charaterization Working Group at W3C has produced a good document analyzing a number of Binary Characterization Use Cases and looking at their properties. The use cases considered include:

• Metadata in Broadcast Systems
• Floating Point Arrays in the Energy Industry
• X3D Graphics Model Compression, Serialization and Transmission
• Web Services for Small Devices
• Web Services within the Enterprise
• Electronic Documents
• FIXML in the Securities Industry
• Multimedia XML Documents for Mobile Handsets
• Intra/Inter Business Communication
• XMPP Instant Messaging Compression
• XML Documents in Persistent Store
• Business and Knowledge Processing
• XML Content-based Routing and Publish Subscribe
• Web Services Routing
• Military Information Interoperability
• Sensor Processing and Communication
• SyncML for Data Synchronization
• Supercomputing and Grid Processing

Santiago is the co-editor of this document and its companion document on XML Binary Characterization Properties. Santiago is also one of the engineers working in the open source implementation of Fast Infoset in the FI project.

This work is licensed under a Creative Commons License.