XML developers often find themselves struggling with multiple versions of the Xerces parser for Java which support different, slightly incompatible versions of SAX, DOM, Schemas, and even XML itself. Xerces can be hiding in a number of different places including the classpath, the jre/lib/endorsed directory, and even the JDK itself. Here’s how you can find out which version you actually have.
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I’ve recently been asked by several people to summarize the state of native XML databases for those interested in exploring this space. IMHO, native XML databases are now roughly where relational databases were circa 1994: solid, proven technology that gets the job done but only if you pay big bucks to do it. However, there’s some promising open source activity on the horizon. To be brief, there are roughly four (maybe five) choices to consider:
David Chapelle writes that
To anybody who’s paying attention and who’s not a hopeless partisan, the war between REST and WS-* is over. The war ended in a truce rather than crushing victory for one side–it’s Korea, not World War II. The now-obvious truth is that both technologies have value, and both will be used going forward.
That’s a nice analogy. Take it one step further though. WS-* is North Korea and REST is South Korea. While REST will go on to become an economic powerhouse with steadily increasing standards of living for all its citizens, WS-* is doomed to sixty+ years of starvation, poverty, tyranny, and defections until it eventually collapses from its own fundamental inadequacies and is absorbed into the more sensible policies of its neighbor to the South.
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There’s a large rebellion over XML config files from programmers who don’t like to type XML and don’t want to learn APIs for processing it. They’d rather limp along with the same scanf code they’ve been using for the last 20 years.
The problem is there really isn’t such a thing as a plain text config file. What there is are specially formatted text files that are easily as complex as the XML equivalent but inconsistent, poorly documented, and easily broken. For instance, consider this extract from LogValidator’s “plain text” config file:
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Co-occurrence constraints are a perennial topic at XML conferences because the usual schema languages (DTDs, W3C Schemas, RELAX NG) can’t handle them. Consequently they’re a fertile source of papers like XML 2006’s keynote from Paolo Marinelli on Co-constraint Validation in a Streaming Context.
However, I mentioned in hallway conversation that I wasn’t sure how common or necessary co-occurrence constraints really were. In fact, I didn’t think I’d ever found one in the real world. Naturally two days later I stumbled across several of them in a very common, very frequent real world example.
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