algorithm to auto-download articles from the internet
what you are asking for is known as web scraping
, if you don't what it is, you can read about it.
can you please clarify your question more, so you can get the right answer.

what programming languages you'll be using, if you are planning on using python, there's a great framework for web scraping called Scrapy.
I found this Parser which does what you are asking for.
finally, you can check this related question.