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XML, XSD, and XSL

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Terminology� World Wide Web Consortium (W3C)

� develops interoperable technologies (specifications, guidelines, software, andtools) to lead the Web to its full potential as a forum for information,commerce, communication, and collective understanding. (www.w3.org)

� Document Object Model (DOM)� a W3C standard API which describes mechanisms for software developers

and Web script authors to access and manipulate parsed XML (and HTML)content. The DOM is both platform-neutral and language-neutral

� Document Type Definition (DTD)� a specification of the elements and attributes that are permitted in an XML

document

� XML Schema� a specification of the elements and attributes that are permitted in an XML

document along with the datatypes for these artifacts

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Terminology (continued)

� Well-formed XML document� an XML document that conforms to basic XML rules

� Valid XML document� a well-formed XML document that conforms to the rules specified in a

DTD

� Simple API for XML (SAX)� a standard interface for event-based XML parsing

� Extensible Stylesheet LanguageTransformations (XSLT)

� A language for transforming XML documents via the application ofstylesheets

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What is XML?

� eXtensible Markup Language�Markup language for describing data�Simpler than predecessor SGML (Standard Generalized Markup

Language)

�More versatile than HTML (HyperText Markup Language)

� Self-describing: XML documents can describeother XML documents (ie. XML schema)

An open standard for defining and sharing data acrossdiverse network topologies Mark Weitzel (IBM)

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Why use XML?

� XML data representation is human-readable,application-neutral, and language-neutralenabling universal interchange of data

� XML documents provide an intuitivemechanism for initializing structured datawithin an application.

� XML standard is open; therefore, costs arenominal

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HTML and XML side by side<table border cellspacing=0

cellpadding=5><tr>

<th>Team name</th><th>Score</th>

</tr><tr>

<td>Clemson</td><td>15</td>

</tr><tr>

<td>NCSU</td><td>17</td>

</tr></table>

<football_game><home><school>NCSU</school><score>17</score></home>

<visitor><school>Clemson</school><score>15</score></visitor>

</football_game>

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XML document syntax

� Element start/end tags<tag1></tag1> or <tag1/><tag1></TAG1> <!– syntax error. XML is case sensitive �

� Attributes<tag1 attribute1=“testValue” /><tag1 enabled /> <!– syntax error. Allowed in HTML not XML �

� Comments<!– This is an XML comment �

� Entity references<tag1 attr1="&Entity1;">

� Processing instructions<?xml version="1.0"?>

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XML document syntax

� Character data sections (CDATA)<![CDATA [<tag1>test</tag1>] ]>

� Document type declarations<!DOCTYPE XmlMappingSpec SYSTEM"abtxmap.dtd" >

<!DOCTYPE XmlMappingSpec SYSTEM"abtxmap.dtd" [<!ENTITY entity1 “testValue1" ><!ENTITY entity2 “testValue2" > ]>

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DTD syntax and terminology

� Element type declarations<!ELEMENT Street (#PCDATA) >

Usage:<Street>29 Oak Street</Street>

� Attribute list declarations<!ATTLIST name firstName CDATA #REQUIRED ><!ATTLIST car maker (Ford | GM | BMW) >

Usage:<name firstName=“George” /><car maker=“Ford” />

<!-- Not valid. Validating parser will flag error �<car maker=“Mercury” />

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DTD syntax and terminology

� Entity declarations<!ENTITY IBM “International Business Machines” ><!ENTITY testDoc SYSTEM “http://mywebsite/testDoc.xml” >

Usage:<Company>&IBM;</Company>

<!– Inline the contents of the testDoc ENTITY �<root>&testDoc;</root>

� Parameter entity declaration<!ENTITY % code_format “CDATA”>

� Notations declarations<!NOTATION Find_Help SYSTEM “Help System” >

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DTD ELEMENT examples� An element with multiple required subelements.

<!ELEMENT main (sub1, sub2, sub3) >

� A subelement (sub2) that occurs once or not at all.<!ELEMENT main (sub1, sub2?) >

� A subelement (sub2) that occurs one or more times.<!ELEMENT main (sub1, sub2+) >

� A subelement (sub2) that occurs zero or moretimes.<!ELEMENT main (sub1, sub2*) >

� An element that contains one of multiple elements.<!ELEMENT main (choice1 | choice2 | choice3) >

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DTD ATTLIST examples� #REQUIRED default indicates that an attribute must be

specified in XML document instance.<!ATTLIST main attr1 CDATA #REQUIRED >

� #IMPLIED default indicates that an attribute is not required bythe XML document instance.<!ATTLIST main attr1 CDATA #IMPLIED >

� #FIXED default indicates an attribute has a fixed value, and noother values are acceptable. Since the attribute value is fixed,it does NOT need to be specified in an instance document.<!ATTLIST main attr1 CDATA #FIXED “FixedValue” >

� Default value supplied. The default value will be used only ifno value is supplied by XML document instance.<!ATTLIST main attr1 CDATA “DefaultValue” >

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Parsing XML (DOM)� DOM parsers read XML into a tree structure

of nodes. Node types are shown below:� Document� DocumentFragment� DocumentType� EntityReference� Element� Attr� ProcessingInstruction� Comment� Text� CDATASection� Entity� Notation

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DOM Element API� getAttribute, setAttribute, removeAttribute,

getAttributeNode, setAttributeNode,removeAttributeNode, hasAttribute

� getAttributeNS, setAttributeNS, removeAttributeNS,getAttributeNodeNS, removeAttributeNodeNS,hasAttributeNS

� getElementsByTagName,getElementsByTagNameNS

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Parsing XML (SAX)� SAX parsers generate parsing events that are

processed by handlers in an application program.Parsers allow users to plug in customimplementations of the SAX interfaces. The SAX2.0 interfaces are:

� Attributes� ContentHandler� DTDHandler� EntityResolver� ErrorHandler� Locator� XMLFilter� XMLReader

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SAX ContentHandlerinterface� characters� endDocument� endElement� endPrefixMapping� ignorableWhitespace� processingInstruction� setDocumentLocator� skippedEntity� startDocument� startElement� startPrefixMapping

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VAST XML parser� XML 1.0 specification

� http://www.w3.org/TR/1998/REC-xml-19980210

� DOM level-2 core interfaces� http://www.w3.org/TR/1998/REC-xml-19980210

� SAX 2.0� http://www.saxproject.org/

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Wedding planner DTD<!-- 3/10/2001 WildAndWackyWeddings.com retains information and performs billing for wedding planners. All wedding planners must provide records in the format specified by this DTD. --><!ELEMENT WeddingPlanner (Address,PhoneNumber,Weddings)><!ATTLIST WeddingPlanner Name NMTOKEN #REQUIRED

id ID #REQUIRED>

<!ELEMENT WeddingPlanners (WeddingPlanner*) ><!ENTITY % AddressMembers 'Street,City,State,Zip' >

<!ELEMENT Address (%AddressMembers;)><!ELEMENT PhoneNumber (#PCDATA) ><!ELEMENT Street (#PCDATA) ><!ELEMENT City (#PCDATA) ><!ELEMENT State (#PCDATA) ><!ELEMENT Zip (#PCDATA) >

<!ELEMENT Weddings (Wedding)* ><!ELEMENT Wedding(Bride,Groom,Date,Time,CeremonyLocation,ReceptionLocation,Caterer,NumberOfGuests,TotalFee,BillingAddress)><!ATTLIST Wedding id ID #REQUIRED ><!ELEMENT Bride (#PCDATA) ><!ELEMENT Groom (#PCDATA) ><!ELEMENT BillingAddress (%AddressMembers;) ><!ELEMENT CeremonyLocation (FacilityName,Address) ><!ELEMENT ReceptionLocation (FacilityName,Address) ><!ELEMENT Date (#PCDATA) ><!ELEMENT Time (#PCDATA) ><!ELEMENT Caterer (#PCDATA) ><!ELEMENT NumberOfGuests (#PCDATA) ><!ELEMENT TotalFee (#PCDATA) ><!ELEMENT FacilityName (#PCDATA) >

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Valid XML document<?xml version="1.0"?>

<!DOCTYPE WeddingPlanner SYSTEM "wedding.dtd" >

<WeddingPlanner Name="J-Lo" id="Planner_1" >

<Address>

<Street>29 Oak St.</Street>

<City>Raleigh</City>

<State>NC</State>

<Zip>99999</Zip>

</Address>

<PhoneNumber>555-4343</PhoneNumber>

<Weddings>

<Wedding id="Ghezzo.G">

<!-- Detailed wedding information removed ... -->

</Wedding>

</Weddings>

</WeddingPlanner>

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VAST XML parser example" Validating parser used to read well-formed XML and verify that thecontents conform to the DTD referenced in the XML."| domDocument domElement |domDocument := AbtXmlDOMParser newValidatingParser parseURI:‘d:\ncsu_2003\wedding1.xml’.domElement := domDocument getElementById: ‘Planner_1’.

" Non-validating parser used to read well-formed XML data. "| domDocument domElements |domDocument := AbtXmlDOMParser newNonValidatingParserparseURI:‘d:\ncsu_2003\wedding1.xml’.domElements := domDocument getElementsByTagName: ‘Address’.

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XML namespaces

An XML namespace is a collection of names, identifiedby a URI reference, which are used in XML documents aselement types and attribute names.In an XML instance document, items are namespace qualified usinga namespace prefix. The reserved word xmlns is used to associatean arbitrary namespace prefix with the actual namespace. Items inthe document instance are prefixed to identify the namespacecontaining their definition.

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XML namespace example<?xml version="1.0"?>

<vastwsd:deployment targetNamespace="urn:SstWSInsurancePolicyInterface"

xmlns:vastwsd="urn:VASTWebServiceDeployment600"

xmlns:vast="Smalltalk"

xmlns:swsipi="urn:Test">

<services>

<service name="SstWSInsurancePolicyInterface" namespace="urn:Test">

<serviceInterfaceClass>SstWSService</serviceInterfaceClass>

<provider type="swsipi:TestProvider">

<vast:provider className=“TestClass" creationMethod="new"/>

</provider>

</service>

</services>

</vastwsd:deployment>

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XML schema� XML schema improves on XML DTD

� XML schemas are coded in XML� XML schema includes type information

allowing object models to berepresented

� The W3C XML Schema Primer is a greatresource for basic information about XMLschema.(http://www.w3.org/TR/xmlschema-0)

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<schema>

� The top-level element of an XML schema document.The schema element typically includes the namespaceassociations required by the schema.

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

xmlns:tns="http://schemas.xmlsoap.org/soap/envelope/"

targetNamespace="http://schemas.xmlsoap.org/soap/envelope/" >

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<element>

� An “instance” of a schema type. An element in XMLschema is much like a variable declaration in typedlanguages like Java.

<xsd:element name=“field1" type="xsd:QName" />

<xsd:element name=“field2" type="xsd:string" minOccurs=“0” />

<xsd:element name=“field3" type="xsd:string” maxOccurs=“unbounded” />

<xsd:element name=“field4" type="xsd:QName" nillable=“true” />

<xsd:element name=“field5" type="xsd:string" default=“TestValue” />

<xsd:element name=“field6" ref=“tns:field1” />

<xsd:element name=“field7" type=“xsd:string” form=“qualified” />

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<attribute>

� Used to represent simple values associated with anXML element. Items represented as attributes cannotcontain other attributes or elements.

<xsd:attribute name=“field1" type="xsd:QName" />

<xsd:attribute name=“field2" type="xsd:string" minOccurs=“0” />

<myElement field1=“tns:FooBar” field2=“testString” />

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<simpleType>

� Used to describe the content of XML elements thatcontain simple data, but no subelements or attributes.

string, normalizedString, token, byte, unsignedByte, base64Binary, hexBinary,integer, positiveInteger, negativeInteger, nonNegativeInteger, nonPositiveInteger,int, unsignedInt, long, unsignedLong, short, unsignedShort, decimal, float, double,boolean, dateTime, duration, date, gMonth, gYear, gDay, gMonthDay, Name,Qname, NCName, anyURI, language, ID, IDREF, IDREFS, ENTITY, ENTITIES,NOTATION, NMTOKEN, NMTOKENS

Below is a list of simpleTypes that are defined in the base XMLschema (http://www.w3.org/2001/XMLSchema). Some of the basetypes are derived from other types.

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<restriction>

� Used to define a new schema type by supplyingconstraints (restrictions) for an existing schema type.

<xsd:simpleType name=“customInteger” >

<xsd:restriction base=“xsd:integer” >

<xsd:minInclusive value=“100” />

<xsd:maxInclusive value=“1000” />

</xsd:restriction>

</xsd:simpleType>

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<extension>

� Used to derive a new schema type by extending theproperties of an existing type (analogous tosubclass).

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<extension> example<complexType name="Address">

<sequence>

<element name="name" type="string"/>

<element name="street" type="string"/>

<element name="city" type="string"/>

</sequence>

</complexType>

<complexType name="USAddress">

<complexContent>

<extension base="ipo:Address">

<sequence>

<element name="state" type="ipo:USState"/>

<element name="zip" type="positiveInteger"/>

</sequence>

</extension>

</complexContent>

</complexType>

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<enumeration>

� Used to provide a list of valid values for anextended type.

<xsd:simpleType name="USState">

<xsd:restriction base="xsd:string">

<xsd:enumeration value="AK"/>

<xsd:enumeration value="AL"/>

<xsd:enumeration value="AR"/>

<!-- and so on ... -->

</xsd:restriction>

</xsd:simpleType>

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<complexType>

� Used to describe XML elements that can containattributes and subelements.

<xsd:complexType name="deploymentType">

<xsd:sequence>

<xsd:element minOccurs="0" name="container" type="tns:containerType" />

<xsd:element minOccurs="0" name="services" type="tns:servicesType" />

</xsd:sequence>

<xsd:attribute name="targetNamespace" type="xsd:anyURI" />

</xsd:complexType>

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<sequence>

� Used to specify a group of elements that must appearin an instance document in the same order that theyare defined in the schema type definition.

<xsd:sequence>

<xsd:element name=“field1" type=“xsd:string" />

<xsd:element name=“field2" type=“xsd:string" />

</xsd:sequence>

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<choice>

� Used to specify that one element or element group outof potentially many will be included in a documentinstance.

<xsd:choice>

<xsd:element name=“field1" type=“xsd:string" />

<xsd:element name=“field2" type=“xsd:string" />

</xsd:choice>

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<all>

� Used to specify a group of elements that may appearonce or not at all in an instance document, and theelements may appear in any order.

<xsd:all>

<xsd:element name=“field1" type=“xsd:string" />

<xsd:element name=“field2" type=“xsd:string" />

</xsd:all>

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<import>

� Used to specify a namespace that is referenced by one or moredeclarations in the schema being defined. An import may specifythe schemaLocation from which the namespace definitions can beretrieved.

<xsd:import namespace=“urn:MyOtherNamespace"schemaLocation="http://www.myserver.com/otherns.xsd" />

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<include>

� Used to pull in definitions from an external resource. Thedefinitions must be in the same namespace as the schema wherethe <include> is specified.

<xsd:include schemaLocation=“moredefinitions.xsd" />

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Other schema tags� annotation, appInfo, attributeGroup,

complexContent, documentation, field, group, key,keyref, length, list, maxInclusive, maxLength,minInclusive, minLength, pattern, redefine, selector,simpleContent, union, unique

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Special attributes (xsi:nil)

Used in an XML instance document to indicate thatthe value of an element is nil

Given the following schema definition:<element name="myValue" type="xsd:string" nillable="true" />

<!-- The presumed value of the 'myValue' element below is the empty string -->

<myValue></myValue>

<!-- The presumed value of the 'myValue' element below is nil -->

<myValue xsi:nil="true"></myValue>

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Special attributes (xsi:type)

Used to enable usage of a derived type where thebase type is expected.

<!– Schema definition for billTo specifies type ‘Address’ �

<billTo xsi:type="ipo:USAddress"> <name>Robert Smith</name>

<street>8 Oak Avenue</street>

<city>Old Town</city>

<state>PA</state>

<zip>95819</zip>

</billTo>

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Wedding planner schema<!-- Schema for wedding planner app. This schema is directly dervied from the wedding.dtd file -->

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

xmlns:tns="urn:WeddingPlanner"

targetNamespace="urn:WeddingPlanner" >

<xsd:complexType name="Wedding">

<xsd:sequence>

<xsd:element name="Bride" type="xsd:string" />

<xsd:element name="Groom" type="xsd:string" />

<xsd:element name="Date" type="xsd:string" />

<xsd:element name="Time" type="xsd:string" />

<xsd:element name="CeremonyLocation" type="tns:Location" />

<xsd:element name="ReceptionLocation" type="tns:Location" />

<xsd:element name="Caterer" type="xsd:string" />

<xsd:element name="NumberOfGuests" type="xsd:int" />

<xsd:element name="TotalFee" type="xsd:decimal" />

<xsd:element name="BillingAddress" type="tns:Address"/>

</xsd:sequence>

<xsd:attribute name="Name" type="tns:string" />

</xsd:complexType>

<!-- Remainder of schema not included in order to save space ����

</xsd:schema>

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XSL (XML Stylesheet Language )

� Enables separation of datacontent and format

� Enables standardized style ofpresentation

� Customizable based uponindividual preferences

� XSL stylesheets are declarative.Each instruction tells the processor “what” toperform in contrast to imperative languages that tellthe processor “how” to perform.

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XML Transformations� Great For Interoperability

Problems� Transforms Data From A Source

Data Format To A Target Format� Source Is XML, Target Is Some

Kind Of Text Format� Target Can Be XML� XSLT Is Used For Transformations� Can Exploit Coalescing Around A

Standard

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XML Transformations

XML + XSLT = HTML

XML + XSLT = XHTML

XML + XSLT = Text

XML + XSLT = XML

XML + XSLT = SVG (Picture)

XML + XSLT = Whatever

(Non-binary)

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XML Transformations

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XSL element names� xsl:stylesheet� xsl:template� xsl:apply-templates� xsl:comment� xsl:pi� xsl:element� xsl:attribute� xsl:value-of� xsl:for-each� xsl:if� xsl:choose� xsl:when� xsl:otherwise� xsl:copy

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XSL example<!-- Only part of this XSL stylesheet is shown here due to space constraints ����

<xsl:template match="football_game">

<html>

<head><title>Game results</title></head>

<body bgcolor="#ffffff" text="#000000">

<table width="100%" border="1" cellspacing="0" cellpadding="4">

<th align="left">Team name</th>

<th align="left">Team score</th>

<xsl:apply-templates select="home"/>

<xsl:apply-templates select="visitor"/>

</table>

</body>

</html>

</xsl:template>

<xsl:template match="home">

<tr>

<td><b><xsl:value-of select="/football_game/home/school"/></b></td>

<td><b><xsl:value-of select="/football_game/home/score"/></b></td>

</tr>

</xsl:template>

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Open source downloads� Xalan XSLT processor (for Java or C++)

http://xml.apache.org/

� Xerces XML validating parser (for Java or C++)http://xml.apache.org/