title: error: Call to a member function startTrans() on a non-object
body: <p>I am using <a href="http://sourceforge.net/projects/powl/" rel="nofollow">pOWL</a> to build a content management system of OWL files. I want to be able to <code>query</code> the OWL files as well as add new instances and classes. However I am stuck. I need to load the OWL file into an OWLModel using pOWL. So I tried:</p>
  
  <pre><code>$base="wine.owl";
  $store = new DefaultPOWLStore(ADODB_DB_DRIVER, "localhost", "powl", "root", "password");
  
  $model = ModelFactory::getOntModel('DBModel','RDFS_VOCABULARY', $base);
  $model = new OWLModel($store, $base);
  $model-&gt;load('wine.owl');
  
  $model -&gt; __construct($store, $base);
  </code></pre>
  
  <p>But I am getting the error:</p>
  
  <pre class="lang-none prettyprint-override"><code>Fatal error: Call to a member function startTrans() on a non-object in C:\Users\xxx\xxx\powl\rdfapi-php\api\model\DbModel.php on line 878
  </code></pre>
  
  <p>The code with the error is:</p>
  
  <pre><code>    if (is_a($model, 'MemModel')) {
              if (is_object($model)){
              echo "&lt;pre&gt;";
              print_r("!!!!!!!");
              echo "&lt;/pre&gt;";
          }
  
          $this-&gt;dbConn-&gt;startTrans();
  </code></pre>
  
  <p>I added the second if clause in an attempt to check if <code>$model</code> is an object, and it passed the clause. But I am not sure if that is the correct way to check if a variable is an object.</p>
  
  <p><strong>UPDATE:</strong> The issue seems to be with <code>dbConn</code> variable, need to find a way to load the model into the DB for <code>dbConn</code> to be defined. Will look tomorrow.</p>