Short snippet summarizing a webpage?

Is there a clean way of grabbing the first few lines of a given link that summarizes that link? I have seen this being done in some online bookmarking applications but have no clue on how they were implemented. For instance, if I give this link, I should be able to get a summary which is roughly like:

I'll admit it, I was intimidated by MapReduce. I'd tried to read explanations of it, but even the wonderful Joel Spolsky left me scratching my head. So I plowed ahead trying to build decent pipelines to process massive amounts of data

Nothing complex at first sight but grabbing these is the challenging part. Just the first few lines of the actual post should be fine. Should I just use a raw approach of grabbing the entire html and parsing the meta tags or something fancy like that (which obviously and unfortunately is not generalizable to every link out there) or is there a smarter way to achieve this? Any suggestions?

开发者_运维百科Update:

I just found InstaPaper do this but am not sure if it is getting the information from RSS feeds or some other way.

Well first of all i would suggest you use PHP with a DOM Parser Class, this will make it a lot easier to get the tag contents you need.

// Get HTML from URL or file
$html = file_get_html('http://www.google.com/');

// Find all paragraphs 
$paragraphs = $html->find('p')

//echo the first paragraph
echo $paragraphs[0];

The problem is a lot of sites have poorly structure html, some are built on tables, the key get around this is that you decide what tags will you consider the website description. I would try to get the meta description tag, if this one does not exist, look for the first paragraph.

You bes tbet is to pull from from the meta description tag. Most blog platforms will stuff the user/system provided excerpt of the post in here as will a lot of CMS platforms. Then if that meta tag isnt present i would just fall back to title or pick a paragraph of appropriate depth.