■ Why my RSS feed changes won't publish?

If you have a blog or regularly updated website content, then you most probably publish a RSS feed to let people know of changes and news. There's nothing special about it, it's a simple XML file with news items including a title, URL (link), description and a publication date. For example here is an item published last week in the xplorer² RSS feed:

<item>
  <title>blog: Unleash your windows search power with xplorer² ultimate</title>
  <link>http://zabkat.com/blog/xplorer2-v2.2-search.htm</link>
  <description>The latest xplorer² version 2.2 ultimate integrates ... blah</description>
  <pubDate>Sun, 07 Oct 2012 10:00:00 GMT</pubDate>
</item>

RSS aggregators, programs like Outlook that consume such feeds and present them to RSS subscribers, periodically check such XML files for modifications. If new content is found, they alert the end user somehow.

Coming from a file management background, I used to believe that the trick was keeping an updated <pubDate> entry. The RSS reader would see a new publication date and notify the user of the news. Well I did it that way for many years and it seemed to work! But every now and then, my newly published items wouldn't be picked up by Outlook (and I imagine other RSS readers). What could be wrong? The feed validator deemed them valid!?

As it turns out, the people who devised the RSS specification weren't coming from file a management perspective. The <pubDate> I used doesn't have anything to do with RSS news item novelty. RSS reader programs use the <link> tag to determine whether items are new or not. It was by accident that most of my news items were published correctly, as each had a unique URL for the blog article. But whenever the item link pointed to something base like the main website, it was discarded as "old news" — regardless of the updated date!

After some googling it transpired that the solution to this puzzle is the <guid> tag. For news items with the same URL, just give them some unique identifier (e.g. number) as such:

	<guid isPermaLink="false"> item_1 </guid>

The exact content of the guid tag isn't important as long as all your items have a different value in there, so that RSS readers can tell them apart.

Peradventure I was also mistaken about why circles have 360 degrees. Always something new to learn! <g>