Exercise related hints

Doc/Sda1/xmlschema.xml

@@ -775,11 +775,29 @@ public class Memo {
               <para>Represent the relational schema being described in <xref
               linkend="invoiceSqlDdl"/> by an XML Schema and provide an
               appropriate example instance. Try to resemble the relational
-              schema as close as possible.</para>
+              schema as close as possible. A possible roadmap:</para>
+
+              <orderedlist>
+                <listitem>
+                  <para>Collect all relational constraints and write them down
+                  informally.</para>
+                </listitem>
+
+                <listitem>
+                  <para>Start from a (just) well-formed <xref
+                  linkend="glo_XML"/> document which allows for entering data
+                  corresponding to the relational model.</para>
+                </listitem>
+
+                <listitem>
+                  <para>Add an <xref linkend="glo_XSD"/> schema file providing
+                  all constraints from your relational model.</para>
+                </listitem>
+              </orderedlist>
             </question>
 
             <answer>
-              <para>A possible schema implementation:</para>
+              <para>A possible schema implementation reads:</para>
 
               <programlisting language="xml">&lt;?xml version="1.0" encoding="UTF-8"?&gt;
 &lt;xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"