Defining Web Document Types - Solutions to Exercises

1. The DTD might be defined as follows:

   <!ELEMENT exam      (code, title, date, questions) >
   <!ELEMENT date      (month, year) >
   <!ELEMENT questions (question, question, question, question, question, question?) >
   <!ELEMENT question  ((part)+) >
   <!ELEMENT part      (#PCDATA|part)* >
   <!ELEMENT code      (#PCDATA) >
   <!ELEMENT title     (#PCDATA) >
   <!ELEMENT month     (#PCDATA) >
   <!ELEMENT year      (#PCDATA) >
   

   A valid instance is:

   <exam>
     <code>IWT</code>
     <title>Internet and Web Technologies</title>
     <date>
       <month>May</month>
       <year>2014</year>
     </date>
     <questions>
       <question><part/></question>
       <question><part/></question>
       <question><part/></question>
       <question><part/></question>
       <question><part/></question>
     </questions>
   </exam>
   

   Instance <exam/> is invalid since the exam element cannot be empty. Instance

   <exam>
     <title>Internet and Web Technologies</title>
     <code>IWT</code>
   </exam>
   

   is invalid since the code element must precede the title element and because the date and questions elements are missing.



2. One DTD is:

   <!ELEMENT programme   (degree, year, results)>
   <!ELEMENT results     ((distinction)?, (merit)?, (pass)?, (fail)?)>
   <!ELEMENT distinction ((name)*)>
   <!ELEMENT merit       ((name)*)>
   <!ELEMENT pass        ((name)*)>
   <!ELEMENT fail        ((name)*)>
   

   where element names without content models specified are assumed to have #PCDATA as their content model. The results categories need not be optional. Alternatively, (name)+ could be used instead of (name)*, but only if results categories are optional; otherwise there is no way of representing an empty list of names.



3. A possible JSON schema is as follows:

   {
       "$schema": "http://json-schema.org/draft-07/schema#",
       "title": "Example",
       "type": "object",
       "properties": {
           "programme": {
               "description": "...",
               "type": "object",
               "properties": {
                   "degree": {"type": "string"},
                   "year": {"type": "string"},
                   "results": {
                       "distinction": {
                           "type": "array",
                           "items": {"type": "string"}
                       },
                       "merit": {
                           "type": "array",
                           "items": {"type": "string"}
                       },
                       "pass": {
                           "type": "array",
                           "items": {"type": "string"}
                       },
                       "fail": {
                           "type": "array",
                           "items": {"type": "string"}
                       }
                   }
               },
               "required": ["degree", "year"]
           }
       }
   }