I put up a new small project now, pricefeed. Basically it creates an RSS 2.0 feed of an Amazon product price, so it can be used for tracking price changes – for example, you want to get a 60GB video iPod but it’s too expensive for you, you use pricefeed to create a feed for this price and then get alerted when it changes.
The RSS <description> field contains a microformatted text (sort of, I just hacked it out since there’s no standard microformat for product information yet) that can be read by the user or parseable by another app. The user sees:
Amazon price for Apple 60 GB iPod with Video Playback Black is now $379.95
And to a parser it would look like:
<p>Amazon price for <span class="title">Apple 60 GB iPod with Video Playback Black</span> is now $<span class="price usd">379.95</span></p>
<p><a class="url" href="http://www.amazon.com/exec/obidos/redirect?tag=niryarivnet-20%26link_code=xm2%26camp=2025%26creative=165953%26path=http://www.amazon.com/gp/redirect.html%253fASIN=B000A3WS8O%2526tag=niryarivnet-20%2526lcode=xm2%2526cID=2025%2526ccmID=165953%2526location=/o/ASIN/B000A3WS8O%25253FSubscriptionId=1CT3AJ9HV6EQ0AG1RZ82">Go to Amazon product page</a></p>
The idea is to delegate as much as possible to the feed reader. For example, there is no database – the price is checked and feed generated when the feed readers access it. Thus no need for cron jobs either. To guarantee new content appears only if the price has changed, the item GUID is based on the price – so the feed reader will only display a new item if the price has changed. A user can look at previous items of the feed and get price history.
Since this is sort of an RSS Tap where new content is quite infrequent, I figured it made sense to allow easy sign up to get notifications via email with RssFwd (my own RSS->Email is running out of quota, and wanted to stick to “no database” ;)). I like being able to sign up and then forget about it, just get an email when there’s new information.
Well, just a little app. Hopefully it demonstrates what I meant in the last few posts and might even be a useful service for some people. I put it up now – please let me know if you run into any issues. (PS: it’s a little rough usablity/looks-wise, it’s more of a proof of concept – so no rounded corners here, yet ;))
UPDATE: Pricefeed is now at Prixfeed.com. RssFwd has been removed for now since the UI depended on XSLT, which Firefox now ignores – you can still use it with the feeds, but it’s not in the UI. Lastly, the iPod URL in the example wouldn’t return a price, since this product is no longer sold as new – the format described remains the same, for example: http://prixfeed.com/?ASIN=0596101880