title: How does scrapy use rules?
body: <p>I'm new to using Scrapy and I wanted to understand how the rules are being used within the CrawlSpider. </p>
  
  <p>If I have a rule where I'm crawling through the yellowpages for cupcake listings in Tucson, AZ, how does yielding a URL request activate the rule - specifically how does it activiate the restrict_xpath attribute? </p>
  
  <p>Thanks.</p>