4) The following XML is a mess! ...

Here it is tidied up:

<?xml version="1.0" ?>
<!DOCTYPE movies [
  <!ELEMENT actor ( #PCDATA )>
  <!ELEMENT movie (actor | title | year)*>
  <!ELEMENT movies (movie+)>
  <!ELEMENT title ( #PCDATA )>
  <!ELEMENT year ( #PCDATA )>
  <!ATTLIST  movie id CDATA #REQUIRED>
]>
<!--This is about movies! -->
<movies>
  <movie id="1">
    <title>The Quest</title>
    <actor>Tom Smith</actor>
    <year>2007</year>
  </movie>
  <movie id="2">
    <title>Summer</title>
    <year>1998</year>
    <actor>Susie Black</actor>
    <actor>Paul White</actor>
  </movie>
  <movie id="3">
    <title>Hello World</title>
  </movie>
</movies>

-------------------------------------------------------------

Selected answers for some of Andrew's DTD exercises 


Options and brackets

	<!ELEMENT country (president|(king,queen?)|queen)>

Payment problem

	<!ELEMENT payment ((card+,cash?)|cash)>

Batches

	<!ELEMENT batch (debit,((debit+,credit)|credit+))>

-------------------------------------------------------------

Selected answers for some of Andrew's XML Schema exercises 

Payment problem

<xs:choice>
  <xs:sequence>
    <xs:element name="card" type="xs:string" maxOccurs="unbounded"/>
    <xs:element name="cash" type="xs:string" minOccurs="0" maxOccurs="1"/>
  </xs:sequence>
  <xs:element name="cash" type="xs:string"/>
</xs:choice>


Batches

<xs:sequence>
   <xs:element name="debit" type="xs:string"/>
   <xs:choice> 
     <xs:sequence>
       <xs:element name="debit" type="xs:string" maxOccurs="unbounded"/>
       <xs:element name="credit" type="xs:string"/>
     </xs:sequence>
     <xs:element name="credit" type="xs:string" maxOccurs="unbounded"/>
  </xs:choice>
</xs:sequence>