DTD- Schema

Doc/Ref/src/Memo.1/memo.xsd

+<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
+   xmlns:vc="http://www.w3.org/2007/XMLSchema-versioning" elementFormDefault="qualified"
+   vc:minVersion="1.0" vc:maxVersion="1.1">
+
+   <xs:element name="memo">
+      <xs:complexType>
+         <xs:sequence>
+            <xs:element name="from" type="xs:string"/>
+            <xs:element name="to" minOccurs="1" maxOccurs="unbounded" type="xs:string"/>
+            <xs:element name="subject" type="xs:string"/>
+            <xs:element name="content" type="xs:string"/>
+         </xs:sequence>
+         <xs:attribute name="date" type="xs:date" use="required"/>
+         <xs:attribute name="priority" type="Priority" use="optional"/>
+      </xs:complexType>
+      
+   </xs:element>
+
+   <xs:simpleType name="Priority">
+      <xs:restriction base="xs:string">
+         <xs:enumeration value="low"/>
+         <xs:enumeration value="medium"/>
+         <xs:enumeration value="high"/>
+      </xs:restriction>
+   </xs:simpleType>
+
+
+</xs:schema>
+
+<!-- A first draft for a memo's grammar -->
+
+<!-- 
+<!ELEMENT memo     (from, to+, subject, content)>
+
+<!ATTLIST memo
+   date     CDATA             #REQUIRED
+   priority (low|medium|high) #IMPLIED>
+
+<!ELEMENT from     (#PCDATA)>
+<!ELEMENT to       (#PCDATA)>
+<!ELEMENT subject  (#PCDATA)>
+<!ELEMENT content  (#PCDATA)>
+
+ -->
\ No newline at end of file

Doc/Ref/src/Memo.1/message.xml

 <?xml version="1.0" encoding="UTF-8"?>
-<!DOCTYPE memo SYSTEM "memo.dtd">
-<memo date="10.02.2006" priority="high">
+
+<memo xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+            xsi:noNamespaceSchemaLocation="memo.xsd" 
+            date="2014-09-24" priority="high">
     <from>M. Goik</from>
     <to>B. King</to>
     <to>A. June</to>