XML and Web Services CS409 Application Services Even Semester 2007.

XML and Web Services

CS409 Application ServicesEven Semester 2007

2

XML Primer

• Extensible Markup Language was introduced in 1998.

• Similar to HTML, but contains an infinite set of elements and attributes.

• All key web services technology are based on XML.

3

Document-Centric XML

• Content is typically meant for human consumption.

• Used to mark up semi structured document.

• Mark up is used to present the information rather than to describe it.

4

Document-Centric XML (2)

• Example, a user guide:<H1>Skateboard Usage Requirements</H1>

To use the SuperFast skateboard you have to have:

<LIST>

<ITEM>A strong pair of legs.</ITEM>

<ITEM>Reasonably long stretch of road surface.</ITEM>

<ITEM>Impulse to impress others.</ITEM>

</LIST>

If you have all of the above, you can proceed to:

<LINK HREF=“Chapter2.xml”>Getting Started</LINK>

5

Data-Centric XML

• Content is typically meant for machine consumption.

• Used to mark up highly structured information.

• Includes many types of tags, organized in a highly-structured manner.

• Order and positioning of tags matter, relative to other tags.

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Data-Centric XML (2)

• Example, a purchase order:<po id=“43871” submitted=“2006-02-01” customerId=“73852”> <billTo> <company>The Soup Restaurant</company> <street>One Microsoft Way</street> <city>Redmond</city> <state>Washington</state> <zipcode>01567</zipcode> </billTo> <order> <item sku=“318-ABC” quantity=“8”> <description>Tall beer glass, plain style</description> </item> <item sku=“898-DEL” quantity=“9”> <description>Table cloth</description> </item> <item sku=“988-MHH” quantity=“600” /> </order></po>

7

XML Standards for Web Services

• XML instances– Rules for creating syntactically correct XML.

• XML Schema– Enables detailed validation and specification of its data

types.

• XML Namespaces– Mechanisms for combining multiple sources XML in a

single document.

• XML processing– Creating, parsing, and manipulating XML from

programming languages.

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XML Instances

• Anatomy of instance:– Declaration– Comments– Elements– Attributes– CDATA section

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XML Instance (2)

• Declaration– Describe the version of XML.– Defined the character encoding.

• Comments– Will be ignored by processing application.

• Example:<?xml version=“1.0” encoding=“UTF-8”>

<po id=“43871” submitted=“2006-02-01” customerId=“73852”>



</po>

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XML Instance (3)

• Elements– Everything between the pairing of start tag and

end tag.– Content types

• Element-only content, consists entirely of nested elements.

• Mixed content, consists of nested elements and text.

• Empty content, start tag immediately followed by end tag.

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XML Instance (4)

• Attributes– A name value pair for the element.– Must use equal sign (=) followed by quote

value.– Attributes begin with xml: is reserved for XML

specification.

• Example<po id=“43871” submitted=“2006-02-01” customerId=“73852”>

<order>

<item sku=“318-ABC” quantity=“8”>

<description xml:lang=“en”>Tall beer glass, plain style</description>

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XML Instance (5)

• CDATA section– Mark a section of text as literal, so it won’t be

parsed as tags and symbols.– The section will be treated as a string of

characters.

• Example:<![CDATA [ <HTML> <BODY> Please don’t treat this as tags but just literal </BODY> </HTML>]]>

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XML Namespaces

• Created to solve recognition and collision problem in XML.

• Is an additional identifier for XML element within a document.

• Namespaces uses Uniform Resource Identifiers (URIs) as identifier.

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XML Without Namespaces<message from=“[email protected]” to=“[email protected]” sent=“2006-02-01”>

<attachment>

<description>The Purchase Order</description>

<item>

<po id=“43871” submitted=“2006-02-01” customerId=“73852”>

<billTo>

<company>The Soup Restaurant</company>

<street>One Microsoft Way</street>

<city>Redmond</city>

<state>Washington</state>

<zipcode>01567</zipcode>

</billTo>

<order>


<description>Tall beer glass, plain style</description>

</item>

</order>

</po>

</item>

</attachment>

</message>

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XML With Namespaces<message from=“[email protected]” to=“[email protected]” sent=“2006-02-01” xmlns=“http://www.xcommerce.com/ns/message”> <attachment> <description>The Purchase Order</description> <item> <po:po id=“43871” submitted=“2006-02-01” customerId=“73852” xmlns:po=“http://www.doddystore.com/ns/po”> <billTo> <company>The Soup Restaurant</company> <street>One Microsoft Way</street> <city>Redmond</city> <state>Washington</state> <zipcode>01567</zipcode> </billTo> <order> <item sku=“318-ABC” quantity=“8”> <description>Tall beer glass, plain style</description> </item> </order> </po:po> </item> </attachment></message>

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XML Schemas

• A meta-language to describe– the structure of XML document.– the mapping of XML syntax to data type.

• Offer an automated an declarative mechanism to validate the contents of XML documents as they are parsed.

• The final specification is defined by the W3C in 2001.

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Basic XML Schema Structure

<?xml version=“1.0” encoding=“UTF-8”>

<xsd:schema xmlns=“http://www.doddystore.com/ns/po”

xmlns:xsd=“http://www.w3.org/2001/XMLSchema”

targetNamespace=“http://www.doddystore.com/ns/po”

<xsd:anotation>

<xsd:documentation xml:lang=“en”>

Purchase order schema for Doddy’s online store

</xsd:documentation>

</xsd:annotation>

<xsd:complexType name=“billTo”>

<xsd:sequence>

<xsd:element name=“company” type=“xsd:string” />

<xsd:element name=“street” type=“xsd:string” />

<xsd:element name=“city” type=“xsd:string” />

<xsd:element name=“state” type=“xsd:string” />

<xsd:element name=“zipcode” type=“xsd:integer” />

</xsd:sequence>

</xsd:complexType>

</xsd:schema>

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Associating Schema to Document


<po:po xmlns:po=“http://www.doddystore.com/ns/po”

xmlns:xsi=“http://www.w3.org/2001/XMLSchema-instance”

xsi:schemaLocation=“http://www.doddystore.com/ns/po

http://www.doddystore.com/schema/po.xsd”

id=“43871” submitted=“2006-02-01” customerId=“73852”

<billTo>

<company>The Soup Restaurant</company>

<street>One Microsoft Way</street>

<city>Redmond</city>

<state>Washington</state>

<zipcode>01567</zipcode>

</billTo>

<order>


<description>Tall beer glass, plain style</description>

</item>

</order>

</po:po>

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XML Schemas Simple Type

• Sets of predefined basic data types.

• String, base64binary, hexBinary, integer, positiveInteger, negativeInteger, nonNegativeInteger, nonPositiveInteger, decimal, boolean, time, dateTime, duration, date, Name, Qname, anyURI, ID, IDREF.

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XML Schemas Simple Type (2)

• Characteristics of simple type (facets):– Length, minLength, maxLength, pattern,

enumeration, whiteSpace, minInclusive, maxInclusive, minExclusive, maxExclusive, totalDigits, fractionDigits.

• Example: <xsd:simpleType name=“poID”>

<xsd:restriction base=“xsd:integer”>

<xsd:minExclusive value=“100”>

<xsd:maxExclusive value=“10000”>

</xsd:restriction>

</xsd:simpleType>

21

XML Schemas Complex Type

• Define complex content model, possibly have attributes and nested children.

• Example: <xsd:complexType name=“poType”>

<xsd:sequence>

<xsd:element name=“billTo” type=“addressType” />

<xsd:element name=“order”>

<xsd:sequence>

<xsd:element name=“item” type=“itemType” maxOccurs=“unbounded” />

<xsd:sequence>

</xsd:element>

</xsd:sequence>

<xsd:attribute name=“customerId” use=“required” type=“xsd:positiveInteger” />

<xsd:attribute name=“submitted” use=“required” type=“xsd:date” />

</xsd:complexType>

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Processing XML

XMLDocument

Character Stream

Serializer

Parser

StandardizedXML APIs

Application

Fig 1. Basic XML Processing Architecture

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Processing XML (2)

• Parsing models– Pull: application always ask the parser.– Push: parser sends notifications to the

application.• Simple API for XML (SAX) standard.

– One-step: parser reads the whole XML doc and generates data structure.

• Document Object Model for XML (DOM) standard.

– Hybrid: combinations of all three above.

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SAX vs DOM

• DOM provides generic object model to represent XML document plus set of interfaces to manipulate it.

• SAX fires callback events into application as it parsed the XML document element by element.

• Both are supported by Java and Microsoft development communities.

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SAX vs DOM (2)

• SAX uses less memory, more efficient for messaging.

• DOM consumes resources, but allows multiple passes through XML document (as if in-memory database or repository).

• Rule of thumb:– Need the document only to do one thing, use

SAX.– Use the document as continuing source of

data, use DOM.

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XML Transformation

• Procedure to interpret contained information in XML document.

• Transformation activities:– Put data into XML document.– Extract data from XML document.– Transform XML document from one schema

format to another.

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XML Transformation (2)

• Standard specification : Extensible Stylesheet Language Transformation (XSLT).

• XSLT is part of XSL (used to transform XML into presentation formats).

• XSLT works with DOM and SAX.

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XML Transformation (3)

• XML Path Language (XPath)– Expression language to link multiple XML

documents.– Used to define search for locating specific

element in XML document, calculation, string manipulations, and evaluating boolean expressions.

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Sample XSLT




<xsl:stylesheet xmlns:”http://www.w3.org/1999/XSL/Transform” version=“1.0”>

<xsl:output method=“text” indent=“yes”>

<xsl:template match=“*”>

<xsl:apply-templates />

</xsl:template>

<xsl:template match=“company”>

Company Name:

<xsl:value-of-select=“.” />

</xsl:template>

<xsl:template match=“street”>

Street Address:


</xsl:template>

<xsl:template match=“zipcode”>

Postal Code:


</xsl:template>

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Sample XSLT (2)

• Transformation result in ASCII text format Company Name: The Soup Restaurant

Street Address: One Microsoft Way

Postal Code: 01567

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Some XML Specifications

• XML 1.0: www.w3.org/TR/REC-xml/• XML Base: www.w3.org/TR/xmlbase/• XML Names: www.w3.org/TR/REC-xml-names/• XML Schema: www.w3.org/TR/xmlschema-1/ and

www.w3.org/TR/xmlschema-2/• XML Path: www.w3.org/TR/xpath• XML Transformation: www.w3.org/TR/xslt• DOM: www.w3.org/TR/DOM-Level-2-Core/

Thank You

Doddy [email protected]

[email protected]

XML and Web Services CS409 Application Services Even Semester 2007.

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