Lets say I have a RSS feed which lists the 3 newest questions on SO. At 1 o'clock, the feed looks like this:

• While making an RSS reader which saves articles, how can I prevent duplicates?
• Convert char array to UNICODE in MFC C++
• How to deploy a Java Swing application with an embedded JavaDB database?

At 2 o'clock, this feed looks like:

• django url from another template than the one associated with the view-function
• While making an RSS reader which saves articles, how can I prevent duplicates?
• Convert char array to UNICODE in MFC C++

(duplicate articles are bold)

I want to download the RSS feed every 5 minutes, parse it and save the articles that aren't already saved, but I do not want duplicates (items that remain in the new, updated feed like the examples above). What can I use to determine if an article is already saved? Thanks