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Perl Module Release: RPC-XML 0.73

Perl Module Release: RPC-XML 0.72

Perl Module Release: RPC-XML 0.71

Perl Module Release: RPC-XML 0.70

Idle Thoughts on Parsing XML (slightly Perlish)

(Side note: There was no Module Monday post this week, as I was too swamped to look for one to cover. Check back next week…)

I’m in the (achingly slow) process of writing a new XML-RPC parser using XML::LibXML. Because (according to their own docs) their SAX support is spotty, I’m letting the library parse the whole message into a DOM object and then using that object to get the request or response. This has proven to be a serious pain in the lower regions.

The XML::Parser approach I’ve had since RPC::XML’s inception is an event-based parser: I use a state-machine/stack approach and push/pop items as needed, based on whether my event is a tag-start, tag-end, text, etc. As a side effect, I validate the document, since the stack/state machine will throw an exception if some event doesn’t fit in to what it is expecting.

Taking a DOM approach means more work, as not only am I drilling down for the data I need, I also have to do some checking for validity as well. (Some might point out that XML::LibXML supports checking document validity against any of a DTD, XML Schema or RelaxNG schema… I’m actually familiar with that. But there is no “real” (i.e., “official”) DTD or schema for XML-RPC for me to use in this case.)

So here’s my observation, which is probably blindingly-obvious to everyone else who’s worked with XML: SAX/event-based parsing is the way to go for processing a whole document, and DOM is better for cherry-picking pieces from different parts of it.

Like I said, probably pretty obvious to the rest of you, but it’s hitting me over the head pretty hard these days.

Perl Module Monday: Test::Formats

I was on vacation most of last week, so this week’s installment of PMM is going to be both short and self-serving. For this week, I’m going to “cheat” and talk about one of my own modules: Test::Formats. (I promise to not make a regular habit of using this feature to promote my own projects.)

This is a pretty simple concept: Rather than using lengthy, confusing regular expressions to test the validity of generated XML documents, why not use the validation already built in to the parser itself? The module isn’t for use on snippets, but then those can usually be tested with much simpler, easier-to-read regexp’s.

The tests you would write with this module are tests of the XML your Perl generates, not necessarily the Perl itself. Alas, time constrains me from any useful examples, so I hope you’ll check out the module itself on CPAN. Next week will be better, I promise!

OSCON Day 2, Part 1: Lightning Talks

I will be giving a lightning talk (possibly two) in the Perl Lightning Talks session at 4:30. The talk I am definitely doing is on ChangeLogML and the Perl module I have for it. If their time and schedule permit, I will also give a talk on my testing module, Test::Formats.