title: Explanation of BASE terminology
body: <p>The <strong>BASE</strong> acronym is used to describe the properties of certain databases, usually NoSQL databases. It's often referred to as the opposite of <a href="http://en.wikipedia.org/wiki/ACID" rel="noreferrer">ACID</a>.</p>
  
  <p>There are only few articles that touch upon the details of BASE, whereas ACID has plenty of articles that elaborate on each of the atomicity, consistency, isolation and durability properties. Wikipedia only devotes <a href="http://en.wikipedia.org/wiki/Eventual_consistency" rel="noreferrer">a few lines</a> to the term.</p>
  
  <p>This leaves me with some questions about <strong>the definition</strong>:</p>
  
  <blockquote>
    <p><b>B</b>asically <b>A</b>vailable, <b>S</b>oft state, <b>E</b>ventual consistency</p>
  </blockquote>
  
  <p>I have interpreted these properties as follows, using <a href="http://queue.acm.org/detail.cfm?id=1394128" rel="noreferrer">this article</a> and my imagination:</p>
  
  <p><strong>Basically available</strong> could refer to the perceived availability of the data. If a single node fails, part of the data won't be available, but the entire data layer stays operational.</p>
  
  <ul>
  <li>Is this interpretation correct, or does it refer to something else?</li>
  <li><strong>Update:</strong> deducing from <a href="https://stackoverflow.com/questions/3342497/explanation-of-base-terminology/3342749#3342749">Mau's answer</a>, could it mean the entire data layer is always accepting new data, i.e. there are no locking scenarios that prevent data from being inserted immediately?</li>
  </ul>
  
  <p><strong>Soft state</strong>: All I could find was the concept of data needing a period refresh. Without a refresh, the data will expire or be deleted.</p>
  
  <ul>
  <li>Automatic deletion of data in a database seems strange to me.</li>
  <li>Expired or stale data makes more sense. But this concept would apply to any type of redundant data storage, not just NoSQL. Does it describe something else then?</li>
  </ul>
  
  <p><strong>Eventual consistency</strong> means that updates will eventually ripple through to all servers, given enough time.</p>
  
  <ul>
  <li>This property is clear to me.</li>
  </ul>
  
  <hr>
  
  <p>Can someone explain these properties in detail?</p>
  
  <p>Or is it just a far-fetched and meaningless acronym that refers to the concepts of acids and bases as found in chemistry?</p>