Author: pobalopalous

Making things go faster — but not worse

At last! A software development manifesto for all of us! Martha Stewart provides some top tips for success in the Autumn edition of wired magazine’s How To Guide. Now, whether you are Agile, Extreme, or recovering from COBOL Fingers you can huddle with the masses under the ‘Making things go faster – but not worse’ banner.

Of course Martha is not a patch on The Toilet Roll Lady who inspired a whole generation of scientists, engineers and public relation gurus. Yes folks, Mary ‘Make and Do’ has a DVD out to capture the nostalgia of yesteryear. Ideal Christmas present for the toilet roll collector in your family.

trailing block elements must have an id attribute

A couple of weeks back some colleagues working on a POC came across this runtime error when invoking a web service through a generated web service proxy client:

trailing block elements must have an id attribute

This exception was being thrown within the web service proxy client when parsing the response from the web service. Using HttpAnalyzer in JDeveloper (versions 10.1.3.1 & 10.1.3.2 were used) we could see that the request was being sent and a response was being received, so clearly nothing wrong with the web service being invoked. Or so we thought…

It turned out that the published WSDL & XSD and the web service implementation were not matching. The XSD for an element in the response said that Address had a maxOccurs=”1″ however, the web service implementation was returning multiple Address elements. The web service proxy client is generated from the WSDL & XSD so it is only expecting one Address element in the response stream, hence the error at runtime.

We had to double check which was correct, and a quick check through documentation showed that the schema had not been updated when the object model had changed. Once that was determined, it was straight forward to correct the schema entry, maxOccurs=”unbounded”, and regenerate the web service proxy client.

So, if you get this obscure ‘trailing block elements must have an id attribute’ error message at runtime double check that the published interfaces (WSDL & XSD) match the implementation.

SCA Diagram stencil for Visio

A visual representation of an SCA composite is a crucial part of composite documentation. Many diagrams are based on section 1.2.1 Diagram used to Represent SCA Artifacts in the SCA Assembly Model Specification. Also worth checking out is a simple, but very useful, description of SCA parts from the Tuscany project.

Since I could not find one, after about 10 minutes of looking, I decided to put together a Visio stencil for SCA composite diagrams which you are free to use. Use the basic Visio connectors to provide links between services, components, references etc. Obviously you can add more service and references to components or composites as you require.

As usual, feedback is welcome, so let me know what you think and if there are any improvements you would suggest.

SOA Governance isn’t about technology either…

Steve Jones summarises a few of the points from a recent ICSOC 2007 debate on SOA Governance and mentions some enforcement ideas in his recent Service Architecture – SOA: SOA Governance isn’t about technology either… article. He makes a good point about people and process.

In the same way that the Rules of the Road is not about what car you drive but about your behaviour and the behaviour of other road users. The reason we have Rules of the Road is because we know, and people recognise, the cause and effect of accidents as well as traffic chaos.

Highlighting SOA anti-patterns (e.g. IBM Article, SOA anti-patterns book) is a good start in bringing to people’s attention poor ‘driver behaviour’. However, as governance is really a business, rather than technical issue, and the business should be the ‘driver’, we also need a higher level exposition (ala Who moved my cheese?) of good business practice around ‘doing IT right’. Any volunteers?