A few weeks ago, Yahoo unveiled a new mash-up service called Pipes. It's sophisticated AJAX-powered graphical interface lets you pull in XML feeds, combine them, filter them and output the result as a customized RSS feed. I've recently used it to create specialized events pages for my blog aggregator. In this series of posts I'll show you how it's done. Each post will be one part of the puzzle.The first tutorial shows how to pull in a Del.icio.us feed.
Step 1: Input tags
The Del.icio.us social bookmarking system runs much of my aggregator:
users see a post they like and bookmark it in Del.icio.us with a
special tag.
The first step in Pipes is to collect the input (right). Pull the
"Text Input" module (above) onto your Pipes work space. This lets you
collect user input. Give it both a name and a prompt. In most instances
it's fine that these be the same as the prompt won't be visible in the
end. It's good to put something down in Debug for later on in the Pipes
process.
Step 2: Construct the RSS call
We take our two input tags and use them to construct an URL by using the "URLBuilder". The base URL is Del.icio.us's RSS feed (http://del.icio.us/rss/). The URL builder adds the user input then the tag input to give us a valid URL (http://del.icio.us/rss/user/tag/).
Step 4: Grab the feed
Yahoo Pipes' "Fetch" module takes that URL input and turns it into an RSS feed. Shown to the right is Fetch with the final "Pipe Output".
See it in action
You can see how this fits together by going to my Del.icio.us Sample page on Pipes. You can make a copy and play with it yourself. Add "&user=username&tag=tagname&_render=rss" to that URL and you've made it a feed.
Okay so I've turned a Del.icio.us RSS feed into... a Yahoo Pipes RSS feed with identical input and output. Well, we're only getting started. Our input tags can be reused for other searches and spliced together inside of a more elaborate Pipe. That's where the fun starts and I'll get there soon.
The other advantage of sending things through Pipes is that we can easily rename fields. Del.icio.us, Flickr and other services often extend RSS standards by including metadata in "dc" fields, an abbreviation for the Dublin Core standards extension. A recent entry from my Del.icio.us feed includes this:
<dc:creator>martin_kelley</dc:creator>
<dc:date>2007-03-15T05:18:53Z</dc:date>
<dc:subject>tech tech.design</dc:subject>
Standard PHP parsers like MagpieRSS and SimplePie often have trouble pulling dc data. With Pipes you can rename the fields you like; in theory that should make them more accessible to the parsers. You can also combine fields and use Pipes' Regex module to operate on them with regular expressions.
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