title: Consider the following set F of functional dependencies on the relation schema r(A,B,C,D,E,F):
body: <p>I have tried to reach out to my instructor with no luck and I really want to understand this process, but no matter how much I read the material I cannot seem to make this fit in my little brain. Can someone please help me with the following questions?</p>
  <pre><code>A--&gt;BCD
  BC--&gt;DE
  B--&gt;D
  D--&gt;A
  </code></pre>
  <blockquote>
  <p>a. Compute B+.</p>
  </blockquote>
  <p>I believe that this one is as follows. Does this seem to be correct?</p>
  <p>B+ denotes closure of B.<br />
  B --&gt; D<br />
  B+ = {BD}<br />
  D --&gt; A<br />
  B+ = {ABD}<br />
  A --&gt; BCD<br />
  B+ = {ABCD}<br />
  BC --&gt; DE<br />
  B+ = {ABCDE}</p>
  <p>All the attributes of the relation can be found by B. So, B is the primary key of the relation.</p>
  <blockquote>
  <p>b. Prove (using Armstrong’s axioms) that AF is a superkey.</p>
  </blockquote>
  <p>I do not understand what to do with F, because it does not show up in the above relationships.</p>
  <blockquote>
  <p>c. Compute a canonical cover for the above set of functional dependencies F; give each step of your derivation with an explanation.</p>
  <p>d. Give a 3NF decomposition of r based on the canonical cover.</p>
  </blockquote>