---+ How to scrape web-pages?

Scraping web-pages for to gather information from them involves several steps.  Prolog may not seem to be the most obvious language for this job, but SWI-Prolog can cope quite well.  Here are the steps:

   1. [[Parse an HTML page][ParseHTML.txt]]
   2. [[Get information from a parsed page][XPath.txt]]
   3. [[Multi-threaded spidering][Spider.txt]]