XML Schema - basic sources of information

XML Schema Specification - http://www.w3.org/XML/Schema
Using W3C XML Schema Tutorial: http://www.xml.com/pub/a/2000/11/29/schemas/part1.html - brief
XML Schema Tutorial - http://www.w3schools.com/schema/default.asp - more comprehensive complete tutorial available at http://www.xfront.com
How to add XML Schema support to Netbeans IDE - http://plugins.netbeans.org/plugin/40292/xmltools4netbeans

XML Schema - motivation

Stronger tool for XML data model specification than DTD
Offers opportunity how to:

Separate type concept (element type for example) from its occurrence (element with particular name) - not possible in DTD
Offers more primitive data types.
Allows to use namespaces.
Allows to specify content model (elements) more accurate way.
Allows new type derivation (inheritance).
Allows modular schema design and schema reuse.
XML syntax of XML Schema

XML Schema - Schema Definition Header

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
      .../...
</xs:schema>

XML Schema - assignment of type to element with the given name

<xs:element name="element_name">
... type definition - placed either right here (so called "local") or referenced one (so called "global")
</xs:element>

XML Schema - Simple Type Definition

Does not contain any child elements. Can be used like either element or attribute type.
Possible to define using an existing type restriction

<xs:simpleType name="TypeName">
 <xs:restriction base="BaseTypeName"> ... </xs:restriction>
</xs:simpleType>

XML Schema - simple type definition - Example 1

Content length restriction

<xs:simpleType name="nameType">
 <xs:restriction base="xs:string"> <xs:maxLength value="32"/>
</xs:restriction> </xs:simpleType>

XML Schema - simple type definition - Example 2

Content restriction using a regular expression

<xs:simpleType name="isbnType">
  <xs:restriction base="xs:string"> <xs:pattern value="[0-9]{10}"/> </xs:restriction>
</xs:simpleType>

XML Schema - simple types - "union"

Approximately correspond to C "union" concept.

Result is a simple type.

Base type and values enumeration can be merged.

Example:

<xs:simpleType name="isbnType">
 <xs:union>
   <xs:simpleType>
    <xs:restriction base="xs:string">
     <xs:pattern value="[0-9]{10}"/>
    </xs:restriction>
   </xs:simpleType>
   <xs:simpleType>
    <xs:restriction base="xs:NMTOKEN">
     <xs:enumeration value="TBD"/>
     <xs:enumeration value="NA"/>
    </xs:restriction>
   </xs:simpleType>
 </xs:union>
</xs:simpleType>

XML Schema - Simple types - values enumeration

Type can be defined as a values list separated by white-spaces.

The number of elements list limitation can used as a next derivation type.

Example

<xs:simpleType name="isbnTypes">
 <xs:list itemType="isbnType"/>
</xs:simpleType>
<xs:simpleType name="isbnTypes10">
 <xs:restriction base="isbnTypes">
   <xs:minLength value="1"/>
   <xs:maxLength value="10"/>
 </xs:restriction>
</xs:simpleType>

XML Schema - complex type definition

<xs:complexType name="TypeName">
 <xs:sequence>
   <xs:element ...> ...
      <xs:attribute ...>
   </xs:element>
 </xs:sequence>
</xs:complexType>

<xs:choice> and <xs:all> can be used instead of sequence.

XML Schema - complex type definition - groups

The group element can be used to define complex type.

Group of elements:

<xs:group name="GroupName">
 <xs:sequence>
      <xs:element ... /> ...
 </xs:sequence>
</xs:group>

<xs:choice> and <xs:all> can be used instead of sequence.

XML Schema - complex type definition - element groups

Attribute group:

<xs:attributeGroup name="AttributesGroupName">
      <xs:attribute ... use="required"/>
      ...
</xs:attributeGroup>

The mandatory occurrence may be specified (use=required).

XML Schema - groups use

Example of elements/attributes groups use:

<xs:complexType name="bookType">
 <xs:sequence>
  <xs:group ref="mainBookElements"/>
  <xs:element name="character" type="characterType" minOccurs="0" maxOccurs="unbounded"/>
 </xs:sequence>
 <xs:attributeGroup ref="bookAttributes"/>
</xs:complexType>

XML Schema - "sequence" compositor

Defines occurrence of elements in the predefined order.

<xs:element name="element_name">
 <xs:complexType>
      <xs:sequence>
       .../...
      </xs:sequence>
      .../...
 </xs:complexType>
</xs:element>

sequence is a content model that allows occurrence of the defined sequence
of child elements.

xs prefix is bound to NS with URL http://www.w3.org/2001/XMLSchema

Either <xs:choice> or <xs:all> can be used instead of<xs:sequence>.

XML Schema - "choice" compositor

Defines the occurrence of only one of the specified child elements or
groups of elements.

<xs:element name="element_name">
 <xs:complexType>
   <xs:choice>
     .../...
   </xs:choice>
   .../...
 </xs:complexType>
</xs:element>

XML Schema - "all" compositor

Defines occurrence of child elements without definition of their order.

May appear on the definition top level only.

The cardinality of child elements can be one at most.

Example:

<xs:complexType name="bookType">
 <xs:all>
   <xs:element name="title" type="xs:string"/>
   <xs:element name="author" type="xs:string"/>
   <xs:element name="character"type="characterType" minOccurs="0" maxOccurs="1"/>
 </xs:all>
 <xs:attribute name="isbn" type="isbnType" use="required"/>
</xs:complexType>

XML Schema - Element simple content

Example:

<xs:element name="book">
 <xs:complexType>
  <xs:simpleContent>
    <xs:extension base="xs:string">
     <xs:attribute name="isbn" type="isbnType"/>
    </xs:extension>
  </xs:simpleContent>
 </xs:complexType>
</xs:element>

XML Schema - mixed element content

The text content (textual child nodes) can not be validated.

The child elements can be validated.

Example:

<xs:element name="book">
 <xs:complexType mixed="true">
  <xs:all>
   <xs:element name="title" type="xs:string"/>
   <xs:element name="author" type="xs:string"/>
  </xs:all>
  <xs:attribute name="isbn" type="xs:string"/>
 </xs:complexType>
</xs:element>

XML Schema - further possibilities

Possibility to specify integrity limitations:

value is unique - xs:unique
value is a key - xs:key
value is a key reference - xs:keyref

XML Schema - Schema annotation

Annotation is a human-readable note (comment) of a schema or its part.

It may contain the processing information (see example - xs:appinfo) as
well.

Next content is not specified (limited) - see example (bind, class, ...)

Example

<xs:annotation>
 <xs:documentation xml:lang="en">Top level element.</xs:documentation>
 <xs:documentation xml:lang="fr">Element racine.</xs:documentation>
 <xs:appinfo source="http://example.com/foo/">
   <bind xmlns="http://example.com/bar/">
    <class name="Book"/>
   </bind>
 </xs:appinfo>
</xs:annotation>

XML Schema - Schema definition reuse

Direct:

<xs:include schemaLocation="character.xsd"/>

With redefinition:

<xs:redefine schemaLocation="character12.xsd">
 <xs:simpleType name="nameType">
  <xs:restriction base="xs:string">
   <xs:maxLength value="40"/>
  </xs:restriction>
 </xs:simpleType>
</xs:redefine>

XML Schema - abstract and final types

abstract - Type can not be instantiated. Can be used for inheritance
derivation only.

final - Type can not be extended/derived by inheritance.

XML Schema - namespaces

Example:

<xs:schema targetNamespace="http://example.org/ns/books/"
      xmlns:xs="http://www.w3.org/2001/XMLSchema"
      xmlns:bk="http://example.org/ns/books/" elementFormDefault="qualified"
      attributeFormDefault="unqualified">
  .../...
</xs:schema>

XML Schema - unspecified elements and attributes

XML Schema allows to use some elements that are not known prior to its
use.

Example:

<xs:complexType name="descType" mixed="true">
 <xs:sequence>
  <xs:any namespace="http://www.w3.org/1999/xhtml"
          processContents="skip" minOccurs="0" maxOccurs="unbounded"/>
 </xs:sequence>
</xs:complexType>

Use xs:anyAttribute for attributes.

XML Schema - schema definition reference

<book isbn="0836217462"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:noNamespaceSchemaLocation="file:library.xsd">

<book isbn="0836217462" xmlns="http://example.org/ns/books/"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="file:library.xsd">

XML Schéma

XML Schema - basic sources of information

XML Schema - motivation

XML Schema - Schema Definition Header

XML Schema - assignment of type to element with the given name

XML Schema - Simple Type Definition

XML Schema - simple type definition - Example 1

XML Schema - simple type definition - Example 2

XML Schema - simple types - "union"

XML Schema - Simple types - values enumeration

XML Schema - complex type definition

XML Schema - complex type definition - groups

XML Schema - complex type definition - element groups

XML Schema - groups use

XML Schema - "sequence" compositor

XML Schema - "choice" compositor

XML Schema - "all" compositor

XML Schema - Element simple content

XML Schema - mixed element content

XML Schema - further possibilities

XML Schema - Schema annotation

XML Schema - Schema definition reuse

XML Schema - abstract and final types

XML Schema - namespaces

XML Schema - unspecified elements and attributes

XML Schema - schema definition reference