title: Facebook Opinion Mining using Java
body: <p>For my graduation I have to develop a Java application for opinion mining on Facebook.
  The topic is opinion mining on the Facebook pages of political parties to compare the opinion of Facebook users to official polls. So it's only public data on public pages.
  I'm using the <code>restfb</code> library to obtain data. I want to obtain posts and comments.</p>
  
  <p>Until now I'm successful in getting the data, but there are some issues which I don't understand:</p>
  
  <ol>
  <li><p>I'm getting data using <code>graphApi</code> calls with URL parameters. With the limit parameter I get a different amount of posts when using an access token provided by the graph explorer, than I get when using an access token provided by logging in with Facebook App data (appId, appSecret). Why is that?</p></li>
  <li><p>Compared to the posts listed on the Facebook Feed, some (public) posts aren't returned at all. What's the reason for this? (As i said, I'm using the limit parameter in a <code>graphApi</code> call)</p></li>
  <li><p>Some of the returned posts seem corrupt. When using the graph explorer the posts look like the following: (I erased to omitted fields)</p>
  
  <pre><code>{
    "id": "id omitted",
    "from": {
      "name": "name omitted",
      "category": "Political party",
      "id": "id omitted"
    },
    "story": "\"\" on their own link.",
    "type": "status",
    "created_time": "2012-10-09T11:13:09+0000",
    "updated_time": "2012-10-09T11:13:09+0000",
    "comments": {
      "count": 0
    }
  },
  </code></pre>
  
  <p>Processing these posts always throws an exception because many data are missing such as comments, likes etc...
  Are these corrupted entries or maybe deleted posts?</p></li>
  </ol>