1 dr alexiei dingli xml technologies x-schema. 2 xml-based alternative to dtd describes the...
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Dr Alexiei Dingli
XML Technologies
X-Schema
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• XML-based alternative to DTD
• Describes the structure of an XML document
• Also referred to as XML Schema Definition (XSD)
What is X-Schema? (1)
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• defines elements that can appear in a document• defines attributes that can appear in a document• defines which elements are child elements• defines the order of child elements• defines the number of child elements• defines whether an element is empty or can include text• defines data types for elements and attributes• defines default and fixed values for elements and attributes
What is X-Schema? (2)
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• XML Schemas are extensible to future additions
• XML Schemas are richer and more powerful than DTDs
• XML Schemas are written in XML
• XML Schemas support data types
• XML Schemas support namespaces
X-Schema vrs DTD
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• describe allowable document content
• validate the correctness of data
• work with data from a database
• define restrictions on data
• define data formats
• convert data between different data types
X-Schema makes it easy to
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• We know the language
• Can be edited with XML editors
• Can be parsed with XML parsers
• Can be manipulated with XML DOM
• Can be transformed with XSLT
Why is it better to use an XML based schema?
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• Ensure secure data communication– 3/11/2004 is the 3rd of November or the 11th of
March?
• Can reuse schemas
• Use one or many in the same document
• Create own data types
Benefits of X-Schemas
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<?xml version="1.0"?>
<note xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="note.xsd">
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>
How to use X-Schema
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<?xml version="1.0"?>
<xs:schema>
<xs:element name="note">
<xs:complexType>
<xs:sequence>
<xs:element name="to" type="xs:string"/>
<xs:element name="from" type="xs:string"/>
<xs:element name="heading" type="xs:string"/> <xs:element name="body" type="xs:string"/>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>
The actual schema
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• Root element of any schema
• May contain attributes
– xmlns:xs="http://www.w3.org/2001/XMLSchema"• Indicate the XSchema namespace
– targetNamespace="http://www.um.edu.mt"• Indicate that the elements defined (to, from, etc) come from the
above namespace
– xmlns="http://www.um.edu.mt"• Sets the default namespace
– elementFormDefault="qualified“• Qualified = all elements can be validated
• Unqualified = only root element can be validated with the namespace
<schema> element
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• A simple element contains only text
• But it can have different types or restrictions (facets)
• <xs:element name="xxx" type="yyy"/>
• <xs:element name=“age" type=“xs:integer"/>
Elements
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• xs:string
• xs:decimal
• xs:integer
• xs:boolean
• xs:date
• xs:time
Element Built-In Types
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<xs:element name="color" type="xs:string" default="red"/>
<xs:element name="color" type="xs:string" fixed="red"/>
Default and Fixed types
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• Simple elements cannot have attributes
• Only complex elements have attributes
• An attribute is declared as a simple type
<xs:attribute name="xxx" type="yyy"/>
Attributes
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<xs:attribute name="lang" type="xs:string" default="EN"/>
<xs:attribute name="lang" type="xs:string" fixed="EN"/>
<xs:attribute name="lang" type="xs:string" use="required"/>
* Optional by default (unless specified)
Default, Fixed and Optional attributes
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<xs:element name="age">
<xs:simpleType>
<xs:restriction base="xs:integer">
<xs:minInclusive value="0"/>
<xs:maxInclusive value="120"/>
</xs:restriction>
</xs:simpleType>
</xs:element>
Restrictions (Facets) - Range
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<xs:element name="car">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:enumeration value="Audi"/>
<xs:enumeration value="Golf"/>
<xs:enumeration value="BMW"/>
</xs:restriction>
</xs:simpleType>
</xs:element>
Restrictions (Facets) – Set 1
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<xs:element name="car" type="cType"/>
<xs:simpleType name="cType">
<xs:restriction base="xs:string">
<xs:enumeration value="Audi"/>
<xs:enumeration value="Golf"/>
<xs:enumeration value="BMW"/>
</xs:restriction>
</xs:simpleType>
Restrictions (Facets) – Set 2
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<xs:element name="letter"> <xs:simpleType>
<xs:restriction base="xs:string"> <xs:pattern value="[a-z]"/>
</xs:restriction>
</xs:simpleType>
</xs:element>
Restrictions (Facets) - Pattern
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Regular expressions example
[A-Z] any letter uppercase
[A-Z][A-Z] two letters uppercase
[a-zA-Z] any letter any case
[xyz] x or y or z
[0-9] any number one digit
([A-Z])+ one or more
([A-Z])* zero or more
male|female either or
[a-zA-Z]{8} exactly 8 characters
Restrictions (Facets) - Patterns
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<xs:element name="address">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:whiteSpace value="preserve"/> </xs:restriction>
</xs:simpleType>
</xs:element>
Restricting white space (1)
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• Value can be
– Preserve• Do not remove white space
– Replace• Replace line feeds, tabs, spaces, and carriage returns with spaces
– Collapse• Same as replace but collapse multiple spaces into one
Restricting white space (2)
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<xs:element name="password">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:minLength value="5"/>
<xs:maxLength value="8"/>
</xs:restriction>
</xs:simpleType>
</xs:element>
Restrictions (Facets) - Length
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Constraint Description
enumeration Defines a list of acceptable values
fractionDigits Specifies the maximum number of decimal places allowed. Must be equal to or greater than zero
length Specifies the exact number of characters or list items allowed. Must be equal to or greater than zero
maxExclusive Specifies the upper bounds for numeric values (the value must be less than this value)
maxInclusive Specifies the upper bounds for numeric values (the value must be less than or equal to this value)
maxLength Specifies the maximum number of characters or list items allowed. Must be equal to or greater than zero
minExclusive Specifies the lower bounds for numeric values (the value must be greater than this value)
minInclusive Specifies the lower bounds for numeric values (the value must be greater than or equal to this value)
minLength Specifies the minimum number of characters or list items allowed. Must be equal to or greater than zero
pattern Defines the exact sequence of characters that are acceptable
totalDigits Specifies the exact number of digits allowed. Must be greater than zero
whiteSpace Specifies how white space (line feeds, tabs, spaces, and carriage returns) is handled
Summarising Restrictions
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1. empty elements
2. elements that contain only other elements
3. elements that contain only text
4. elements that contain both other elements and text
Complex Elements
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<xs:element name="product">
<xs:complexType>
<xs:attribute name="prodid" type="xs:positiveInteger"/>
</xs:complexType>
</xs:element>
Ex
<product prodid="1345" />
Complex Empty Elements
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• Contains only other elements
<xs:element name="person">
<xs:complexType>
<xs:sequence>
<xs:element name="firstname" type="xs:string"/> <xs:element name="lastname" type="xs:string"/> </xs:sequence>
</xs:complexType>
</xs:element>
Complex Elements Only
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<person>
<firstname>John</firstname>
<lastname>Smith</lastname>
</person>
Complex Elements Only Ex
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<xs:element name="shoesize">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:integer">
<xs:attribute name="country" type="xs:string" />
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
Eg
<shoesize country="france">35</shoesize>
Complex TextOnly Element
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<xs:element name="letter">
<xs:complexType mixed="true">
<xs:sequence>
<xs:element name="name" type="xs:string"/>
<xs:element name="orderid" type="xs:positiveInteger"/>
<xs:element name="shipdate" type="xs:date"/>
</xs:sequence>
</xs:complexType>
</xs:element>
Complex Mixed Content
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• Order indicators:– All
• All must occur but in any order
– Choice• Either or can occur
– Sequence• Must appear in a specified sequence
• Occurrence indicators:– maxOccurs– minOccurs
• Group indicators:Group elements or attributes together and allow for reuse
– Group name – attributeGroup name
7 Indicators
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<xs:element name="person">
<xs:complexType>
<xs:all>
<xs:element name="firstname" type="xs:string"/>
<xs:element name="lastname" type="xs:string"/>
</xs:all>
</xs:complexType>
</xs:element>
All, Choice, Sequence indicator
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<xs:element name="person">
<xs:complexType>
<xs:sequence>
<xs:element name="child_name" type="xs:string"
maxOccurs="10" minOccurs="0"/>
</xs:sequence>
</xs:complexType>
</xs:element>
Occurrence indicator
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<xs:element name="person">
<xs:complexType>
<xs:sequence>
<xs:element name="child_name" type="xs:string"
maxOccurs="10" minOccurs="0"/>
<xs:any minOccurs="0"/>
</xs:sequence>
<xs:anyAttribute/> </xs:complexType>
</xs:element>
*allows for any element or attribute but it has to be defined just the same in another XSchema
<any> and <anyAttribute>
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<xs:element name="name" type="xs:string"/>
<xs:element name=“isem" substitutionGroup="name"/>
Allows for …
<customer>
<isem>John</isem>
</customer>
Substitutions
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Name Description
ENTITIES
ENTITY
ID A string that represents the ID attribute in XML (only used with schema attributes)
IDREF A string that represents the IDREF attribute in XML (only used with schema attributes)
IDREFS
language A string that contains a valid language id
Name A string that contains a valid XML name
NCName
NMTOKEN A string that represents the NMTOKEN attribute in XML (only used with schema attributes)
NMTOKENS
normalizedString A string that does not contain line feeds, carriage returns, or tabs
string A string
token A string that does not contain line feeds, carriage returns, tabs, leading or trailing spaces, or multiple spaces
String Datatype
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Name Description
date Defines a date value
dateTime Defines a date and time value
duration Defines a time interval
gDay Defines a part of a date - the day (DD)
gMonth Defines a part of a date - the month (MM)
gMonthDay Defines a part of a date - the month and day (MM-DD)
gYear Defines a part of a date - the year (YYYY)
gYearMonth Defines a part of a date - the year and month (YYYY-MM)
time Defines a time value
Date Datatype
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Name Description
byte A signed 8-bit integer
decimal A decimal value
int A signed 32-bit integer
integer An integer value
long A signed 64-bit integer
negativeInteger An integer containing only negative values ( .., -2, -1.)
nonNegativeInteger An integer containing only non-negative values (0, 1, 2, ..)
nonPositiveInteger An integer containing only non-positive values (.., -2, -1, 0)
positiveInteger An integer containing only positive values (1, 2, ..)
short A signed 16-bit integer
unsignedLong An unsigned 64-bit integer
unsignedInt An unsigned 32-bit integer
unsignedShort An unsigned 16-bit integer
unsignedByte An unsigned 8-bit integer
Numeric Datatype
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Example
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• Define an XML Vocabulary for a Toaster Markup Language (TML) using XSchema
• It must support features such as:– Print message on toast– Display on LCD– Time stamp
Exercise
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Questions?