Irvine COP 4814

COP 4814 Florida International University

Kip Irvine

XML Schema Basics, and Defining Simple Types

Updated: 2/23/2016 Based on Goldberg, Chapters 9 & 10

XML Schema Overview

• Also known as XML Schema Definition (XSD) • Specifies the structure of valid XML documents

– defines a set of elements, their relationships to each other, and the attributes that they can contain.

• Designed to address shortcomings of DTDs – has a system of data types – lets you define global and local elements – likely to replace DTDs in the future as the standard

schema language

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Latest info: http://w3.org/XML/Schema

Data Type Categories

• Atomic type – XML element that only contains text

• List type – collection of items

• Complex type – XML element that contains child elements and/or

attributes

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Sample XML File & Schema

<?xml version="1.0"?> <wonder> <name>Colossus of Rhodes</name> <location>Greece</location> <height>107</height> </wonder>

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<?xml version="1.0"?> <element name="wonder"> <complexType> <sequence> <element name="name" type="string"/> <element name="location" type="string"/> <element name="height" type="string"/> </sequence> </complexType> </element>

incomplete Schema file

Complete Schema File

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<?xml version="1.0"?> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"> <element name="wonder"> <complexType> <sequence> <element name="name" type="string"/> <element name="location" type="string"/> <element name="height" type="string"/> </sequence> </complexType> </element> </xs:schema>

Linking the XML Document

To the XML Schema file:

<?xml version="1.0"?>

<wonder xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="09-06.xsd" >

<name>Colossus of Rhodes</name>

<location>Greece</location>

<height>107</height>

</wonder>

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Web location, network path, or local file

Visual Studio doesn’t need this extra line—you can just assign a value to the Schemas property of the XML file.

XML Annotations

Structured comments that can be processed by XML parsers. Can appear anywhere, multiple times. <xs:annotation>

<xs:documentation>

This XML Schema will be used to validate documents from the student registration system.

</xs:documentation>

</xs:annotation>

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Atomic Datatypes

• Contain a single value (cannot be divided). • Based on one of the built-in types.

– Example: type="xs:string • Restrictions can be included on their ranges and

character patterns, allowing you to create subtypes. • Type categories:

– string, integer, boolean, date, decimal, etc.

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Simple Types

Some of the more common types: <xs:element name="height" type="xs:string"/>

<xs:element name="year_built" type="xs:integer"/>

<xs:element name="cost" type="xs:decimal"/>

<xs:element name="is_standing" type="xs:boolean"/>

<xs:element name="image" type="xs:anyURI"/>

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Web location, network path, or local file

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Standard Date/Time Formats

• xs:date: yyyy-mm-dd "2005-04-26"

• xs:time: hh:mm:ss "16:21:00"

• xs:dateTime yyyy-mm-ddThh:mm:ss "2005-04-26T16:21:00"

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xs:duration

• xs:duration: – PnYnMnDTnHnMnS

• 3 months, 4 days, 6 hours, 17 minutes: – "P3M4DT6H17M"

• 90 days: – "P90D"

• 4 days and 6 hours: – "P4DT6H"

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Other Date Types

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Type Examples

xs:gYear "1965"

xs:gMonth "--04" (April)

xs:gYearMonth "1965-04" (April 1965)

xs:gMonthDay "--0426" (April 26)

xs:gDay

"---26" (26th day)

Custom Type

• Identify the XML element you wish to define • The "base" attribute identifies an existing type. • Example: string of <= 1024 characters: <xs:element name="story"> <xs:simpleType> <xs:restriction base="xs:string"> <xs:length value="1024"/> </xs:restriction> </xs:simpleType> </xs:element>

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this custom type is anonymous

Named Custom Type

• Alternatively you can add a name attribute to the xs:simpleType element:

<xs:element name="story"> <xs:simpleType name="story_type"> <xs:restriction base="xs:string"> <xs:length value="1024"/> </xs:restriction> </xs:simpleType> </xs:element>

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Applying a Custom Type

• The same named type can be used multiple times: <xs:element name="story" type="story_type"/> <xs:element name="summary" type="story_type"/> <xs:element name="another_story" type="story_type"/>

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Limiting Values to a Range

• Use xs:minInclusive and xs:maxInclusive:

<xs:element name="student_age">

<xs:simpleType>

<xs:restriction base="xs:integer">

<xs:minInclusive value="10">

<xs:maxInclusive value="120">

</xs:restriction>

</xs:simpleType>

</xs:element>

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Also possible: minExclusive, maxExclusive

Set of Possible Values

Use xs:enumeration

<xs:element name="student_level"> <xs:simpleType> <xs:restriction base="xs:string">

<xs:enumeration value="undergraduate"/> <xs:enumeration value="graduate"/> <xs:enumeration value="unclassified"/>

</xs:restriction> </xs:simpleType> </xs:element>

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Specifying an Exact Length

Example: <xs:element name="panther_id"> <xs:simpleType> <xs:restriction base="xs:string">

<xs:length value="7"/>

</xs:restriction> </xs:simpleType> </xs:element>

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Also possible: xs:minLength, xs:maxLength

Specifying a Matching Pattern

• Uses regular expression syntax • Suppose the account_id element must contain

AB, followed by digits:

<xs:element name="account_id"> <xs:simpleType> <xs:restriction base="xs:string">

<xs:pattern value="AB\d+"/>

</xs:restriction> </xs:simpleType> </xs:element>

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Deriving a List Type

• When the XML file contains a list of values – Example: dates when a student declared or

changed majors:

<xs:element name="catalog_dates"> <xs:simpleType>

<xs:list itemType="xs:date"/>

</xs:simpleType> </xs:element>

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this custom type is anonymous

Deriving a Named List Type

Use a named type if you plan to apply it more than once. <xs:simpleType name="dateList">

<xs:list itemType="xs:date"/>

</xs:simpleType> .

<!-- create instances: -->

<xs:element name="catalog_dates" type="dateList"/>

<xs:element name="enrollment_dates" type="dateList"/>

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Summary

• Use built-in types when you have no particular restrictions on the values

• Use simple (atomic) derived types to control ranges and lengths

• Use list types for repeated items • Chapter 11 explains how to create complex types.

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