title: Difference between HDF5 file and PyTables file
body: <p>Is there a difference between <code>HDF5</code> files and files created by <code>PyTables</code>? </p>
  
  <p><code>PyTables</code> has two functions <code>.isHDFfile()</code> and <code>.isPyTablesFile()</code> suggesting that there
  is a difference between the two formats.</p>
  
  <p>I've done some looking around on Google and have gathered that PyTables is built on top of HDF, but I wasn't able to find much beyond that.  </p>
  
  <p>I am specifically interested in interoperability, speed and overhead.</p>
  
  <p>Thanks.</p>