Add support for allowing namespace prefixes in rule definitions

UNDER CONSIDERATION

Given a header of:

considering allowing the use of prefixes in the rule definitions. So a change from something like:
/rss/channel/[http://search.yahoo.com/mrss/]thumbnail/url

to:
/rss/channel/[media]thumbnail/url

PROBLEM

SJXP has always tried to stay away from allowing prefixes because they are not guarunteed to be static. You could write a parser that always parses "[media]/thumbnail/url" and half the feeds you try and parse map the Yahoo Media URI to the prefix "m" instead of "media".

In all these cases, the parse you write with SJXP will silently fail and you'll have no idea why. Unfortunately there is no way for SJXP to know how to map the prefix you have in your url to a redefined name in the XML source.

I have long fought against adding this feature because the downside introduced with it can be maddening to anyone using the library.

The following is a mock scenario to illustrate the point...

SCENARIO

Android developer Frank uses SJXP to write an RSS-based mobile app called "Feedorama" that is a really cutting edge RSS feed reader.

In the app Frank has defined all the rules for RSS feed parsing using the prefixes for really popular and commonly included namespaces like "dc" for Dublin Core, "media" for Yahoo Media and so on.

Frank tests his app with 50 or so feeds and it works great, so he releases it on the Android Marketplace for $1.99

A week goes by and Frank starts getting 1 and 2 star reviews on the marketplace with comments like "Doesn't work, this is crap!" and "Won't load half my feeds!"

Frank has no idea what is going on and no one is filing bug reports with him, but his product is getting buried now with the bad reviews.

After finally getting some test URLs from some unhappy customers demanding refunds, Frank tests the RSS feeds out and sure enough, verifies that nothing happens... none of the information (or at least the information represented by prefixed-tags) is getting pulled in!

After downloading the source to SJXP and stepping through it with a debugger, he FINALLY sees why... all these "failing" documents define custom prefixes, like "meta" for Dublin Core and "ym" for Yahoo Media.

Frank curses at SJXP; screaming himself horse and emailing the author (me) death threats.

Frank has no idea that SJXP can also use the full URIs in the rule definitions, so he just decides SJXP is "@#*&!%-ing broken" and switches out the parser to some other parser that he now has to hand-write from scratch, adding weeks to his development schedule.

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That may be a bit of a stretch, but hopefully it clarifies why I likely won't add this feature; I feel like it will help people shoot themselves in the foot with the complexities of XML too easily.