title: AppEngine database-layout, which is easy to expand
body: <p>I need a database layout, which is highly expandable. I have a super class "station" which will have a unique id and multiple attributes.</p>
  
  <pre><code>station {
      unique_identifier: id
      ...
  }
  </code></pre>
  
  <p>most attributes look like this</p>
  
  <pre><code>station_attribute_item {
      referenced_station: id,
      value: double,
      date: date
  }
  </code></pre>
  
  <p>So you can visualize an attribute as an item of a list with a date member and a value.</p>
  
  <p>Thus if I need a new attribute, I add a new class and that's it? All I have to do is query for a new attribute?</p>
  
  <pre><code>new_station_attribute {
      referenced_station: id
      value1: string
      value2: double
      start: date
      end: date
  }
  </code></pre>
  
  <p>Edited:</p>
  
  <p>Is this data-layout feasible on the AppEngine infrastructure?</p>