title: Creating DTD (Document Type Definition) file using atrributes, fixed, required, implied etc
body: <p>We only talk about DTD and XML in class for 2 days and i have this assignment not sure if im doing it right or did everything that has been asked. Atleast i try, any help will be appreciated!!</p>
  
  <p>Assignment
  You have been asked to represent airport data where an airport has  required attributes name and location;  and an implied attribute famous_assoiciation.  The famous_assoication attribute is the name of a famous person after whom the airport has been named.  An  airport is composed of one or more hangers.  Each hanger has a number, location and a set of 0 or more associated airlines.  Each hanger also has a fixed attribute, length, of 2 miles.   An  airline has a name, one of more  types of  aircraft fleets (where a fleet contains one or more planes).   A plane has a manufacturer, model, vin and seat_capacity.  A plane also has attribute color with a default value of “silver”</p>
  
  <p>You may assume that all data in this system is of type CDATA</p>
  
  <p>This is what i did...</p>
  
  <pre><code>&lt;?xml version = "1.0" encoding ="utf-8"?&gt;
  
  &lt;!ELEMENT airport (hanger+)&gt;
   &lt;!ELEMENT hanger (number, location, airline*)&gt;
   &lt;!ELEMENT number (#PCDATA)&gt;
   &lt;!ELEMENT location (#PCDATA)&gt;
   &lt;!ELEMENT airline (name, aircraft fleets+)&gt;
   &lt;!ELEMENT name (#PCDATA)&gt;
   &lt;!ELEMENT aircraft fleets (plane+)&gt;
   &lt;!ELEMENT plane (manufacturer, model, vin, seat_capacity)&gt;
   &lt;!ELEMENT manufacturer (#PCDATA)&gt;
   &lt;!ELEMENT model (#PCDATA)&gt;
   &lt;!ELEMENT vin (#PCDATA)&gt;
   &lt;!ELEMENT seat_capacity (#PCDATA)&gt;
  
  
   &lt;!ATTLIST airport name CDATA #REQUIRED&gt;
   &lt;!ATTLIST airport location CDATA #REQUIRED&gt;
   &lt;!ATTLIST airport famous_assoiciation CDATA #IMPLIED&gt;
   &lt;!ATTLIST plane color CDATA #FIXED "silver"&gt;
   &lt;!ATTLIST hanger length CDATA #FIXED "2 miles"&gt;
  </code></pre>