XML Schi
Relax NG
PB138 - Markup Languages
Tomas Pitner March 8, 2013
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XML Schema   Relax IMG
0 XML Schema
0 Relax NG
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XML Schi
Relax NG
urces 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/partl.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://blogs.oracle.com/geertj an/entry/xml_schema_
editor_in_netbeans)
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XML Schema   Relax IMG
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   Relax IMG |
XML Schema - Schema Definition Header
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
.../... </xs:schema>
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XML Schema   Relax NG |
XML Schema - assignment of type to element with the given name
<xs:element name="ElementName">
... type definition - placed either right here (so called </xs:element>
XML Schema   Relax NG |
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>
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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>
- simple type definition - Example 2
Content restriction using a regular expression
<xs:simpleType name="isbnType">
<xs:restriction base="xs:string"> <xs:pattern value=" [0-</xs:simpleType>
XML Schi
Relax NG
- 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:NMTDKEN"> <xs:enumeration value="TBD"/> <xs:enumeration value="NA"/> </xs:restriction>
XML Schema   Relax NG |
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="isbnTypeslO"> <xs:restriction base="isbnTypes"> <xs:minLength value="l"/> <xs:maxLength value="10"/> </xs:restriction> </xs:simpleType>
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e definition
<xs:complexType name: <xs:sequence>
<xs:element ...> <xs:attribute </xs:element> </xs:sequence> </xs:complexType>
"TypeName">
<xs:choice> and <xs:all> can be used instead sequence.
e 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 sequence.
XML Schema   Relax NG |
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   Relax IMG
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" minOcci </xs:sequence>
<xs:attributeGroup ref="bookAttributes"/> </xs:complexType>
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XML Schema   Relax NG |
XML Schema - "sequence" compositor
Defines occurrence of elements in the predefined order.
<xs:element name="ElementName"> <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 jxs:choice£ or jxs:a11^ can be used instead ofjxs:sequence£.
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XML Schema   Relax NG |
XML Schema - "choice" compositor
Defines the occurrence of only one of the specified child elements or groups of elements.
<xs:element name="ElementName"> <xs:complexType> <xs:choice>
.../... </xs:choice> .../... </xs:complexType> </xs:element>
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XML Schema   Relax NG |
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" minOcci </xs:all>
<xs:attribute name="isbn" type="isbnType" use="required"/; </xs:complexType>
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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>
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XML Schema   Relax NG |
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>
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XML Schema   Relax NG |
XML Schema - further possibilities
Possibility to specify integrity limitations:
» value is unique - xs:unique
• va I ue is a key - xs: key
• value is a key reference - xs:keyref
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- 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:doc <xs:documentation xml:lang="fr">Element racine.</xs:docume <xs:appinfo source="http://example.com/foo/"> <bind xmlns="http://example.com/bar/">
<class name="Book"/> </bind> </xs:appinfo>
</xs :annotation> < s ►   5 ^^p.
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Direct:
<xs:include schemaLocation="character.xsd"/> With redefinition:
<xs:redefine schemaLocation="characterl2.xsd"> <xs:simpleType name="nameType"> <xs:restriction base="xs:string">
<xs:maxLength value="40"/> </xs:restriction> </xs:simpleType> </xs:redefine>
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- 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   Relax IMG
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/" elementFormDe attributeFormDefault="unqualified"> .../...
</xs:schema>
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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="\
</xs:sequence> </xs:complexType>
Use xs:anyAttribute for attributes.
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- 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 Schema:
• too complicated (more than a 200 pages of specification)
• May be ambiguous in some situations.
• Tries to cover all applications area (documents, databases and all in between).
• Only hardly to fully implementable.
• See
http://www.xml.com/lpt/a/2002/01/23/relaxng.html for more.
XML Schema   Relax IMG |
nary information sources
Based on RELAX designed by OASIS-OPEN:
• http://www.oasis-open.org/committees/relax-ng
• Validators:
• Jing (http://code.google.eom/p/jing-trang/)
• Libxml2(http://www.xmlsoft.org/)
• RNV (http://www.davidashen.net/rnv.html) - supports the compact syntax only
• See http://relaxng.0rg/#validators for more.
• XML editors supporting Relax NG
• Firedocs (http://firedocs.org) - Firefox plug-in
• XML Operator (www.xmloperator.net) - OSS (BSD Licence)
» xml editor (http://www.oxygenxml.com/) - commercial
• ...
• See http://relaxng.0rg/#editors for more