Is there markup to tell Google our site is a forum?

Selected answers from the Dumb SEO Questions Facebook & G+ community.

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  Justin Y: I'm not sure, I've never looked into this myself. I would like to think that it depends on the life of the forum, most forums that appear in SERPs with sitelinks like that have years of archives. 
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  Ashish Ahuja: do you show related questions on the question page itself and if they are relevant google will show these in some time
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  Ranu Jain: These are "Indented Results". Here is how you can achieve this:
  
  1) Have a page that already has a top 10 ranking for that keyword/ keyphrase.
  
  2) Create a second page on the same website that links to the first page that has the top 10 ranking. Optimize the second page for the same/ similar keyword/ keyphrase as page one but use different content.
  
  3) Link from the first page to the second page with your keyword phrase in the anchor text. If possible, use a contextual link within a body of text rather than a site-wide navigational link.
  
  4) Get inbound links for the second page. Depending on the competition for the keyword, a few high-quality links can be enough to get the indented result.
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  Mike Stetzer: I appreciate the feedback everyone!
  
  I think this also has to do with Google's understanding that Yahoo Answers is a Q&A site. Maybe some sort of custom parsing going on. ;
  
  Ranu, I think I'm going to reevaluate how our Related Questions/Related Answer field is pulled. Thanks again for the feedback!
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  W.E. Jonk: From the expert panel in this weeks SEO Questions hangout on air on 02:25:14 into the YouTube video: https://dumbseoquestions.com/q/is_there_markup_to_tell_google_our_site_is_a_forum
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  Mike Stetzer: Very cool that you guys brought up my question on air. Thanks!