title: Better choice between RDBMS and LDAP
body: <p>I know that there are several similar posts available discussing the same but I didn't find the answer for my case.</p>
  
  <p>I have just basic idea of LDAP which we can get through google search like it is a directory database, used for hierarchical data and optimised for reads than writes. And of course LDAP is protocol to access the database.</p>
  
  <p>A little background of problem:</p>
  
  <ol>
  <li>We have to create a presence service(publish-subscribe) for which we
  have to choose between a directory based DB and an RDBMS.</li>
  <li>The DB will be on cloud so if RDBMS is chosen it will be exposed as
  a Web Service and if a directory based is chosen it will be accessed
  via LDAP.</li>
  </ol>
  
  <p><em>Service is a pub-sub model where each user may be a publisher with many subscriber and it may itself be subscriber. So, it is m</em>n relationship.*</p>
  
  <p>Now, I have two questions regarding the same.</p>
  
  <ol>
  <li>Can we model this in directory based database? I looked through the
  schemas but could not figure out how to do that.</li>
  <li>Second question is regarding the approach of accessing the data i.e.
  using LDAP or using web service. I don't know what are the
  advantages/disadvantages of using LDAP over usage of web service.</li>
  </ol>
  
  <p>Appreciate any help.</p>
  
  <p>Thanks</p>