Web Tech Class 7

8/8/2019 Web Tech Class 7

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Mr. Debojit Boro

Assistant Professor,Tezpur University,Napaam,Tezpur-784028

Web Technology

Batches:

M.Tech. 2nd Semester

B.Tech 6th Semester

B.Tech. 8th Semester

MCA 4th Semester

B.Tech. Electronics 8th Semester

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Topics for today

XSLT

XPATH

XQUERY

XMLSCHEMA

Browser Architecture

Mr. Debojit Boro

Assistant Professor,Tezpur University,Napaam,Tezpur-7840282


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Various components of XML


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XSLT (Extensible Style Sheets

Language Transformations)

XSLT is a language for transforming XML documentsinto XHTML documents or to other XML documents

XSLT uses XPath to find information in an XMLdocument


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XSLT uses XPath to define parts of the

source document that should match one ormore predefined templates. When a match isfound, XSLT will transform the matching partof the source document into the resultdocument.

For Learning the XSLT refer to the previous

.ppt (Web Tech Class 6.ppt)


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XPATH

This is used to navigate through the elements andattributes in XML document

XPath is a syntax for defining parts of an XML document

XPath uses path expressions to navigate in XML

documents

XPath contains a library of standard functions

XPath is a major element in XSLT

XPath is a W3C recommendation

Over 1000 built-in standard functions like date-timecomparision

This XPATH is used in XSLT documents


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XPATH uses seven kinds of nodes

1) element

2) attribute

3) text

4) namespace5) processing-instruction

6) comment

7) document nodes


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XPATH Syntax

XPATH uses path expressions to select nodes or node-sets ina XML document

Expression Description

nodename Select all child nodes of the named nodes/ Selects from the root node

// Selects nodes in the document from thecurrent node that match the selection nomatter where they are in the document

. Selects the current node

.. Selects the parent of the current node

@ Selects attributes


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1010

Juliana Dantas

IT

25000

Pedro Almeida

1011

>Leonardo Nasimeta

IT

30000

Pedro Almeida

Example ofXML file emp.xml referencing emp.xsl

Note*: We ll be refering to this example on all cases


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Path Expressions

Eg.1. Select all the child nodes of the PAYROLL element

Path Expression: PAYROLL

Eg.2. Select all EMPLOYEE elements that are children of PAYROLL

Path Expression: PAYROLL/EMPLOYEE

Eg.3

Select all attributes that are named status

Path Expression: //@status


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Predicates

Predicates are used in the path expressions to find a specific node or anode that contains a specific value. They are used within the brackets

[ predicates]

Eg.1. Select the first EMPLOYEE element that is the child of the PAYROLL

element.

Path Expression: /PAYROLL/EMPLOYEE[1]

Eg.2. Select the first two EMPLOYEE elements that are children of thePAYROLL element

Path Expression: /PAYROLL/EMPLOYEE[position()


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Some Predicates used are:

Last() Position()

Note*: Remember Predicates can beattributes or even elements itself. Its just away of defining a specific condition


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For selecting unknown nodes

Wildcard characters are also used in XPATH expressions such as

* - Matches any attribute nodes

eg. Select all the child nodes of the PAYROLL element/PAYROLL/*

@* - Matches any attribute nodes

eg. Select all NAME elements which have any attribute//NAME[@*]

Node() Matches any nodes


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Node sets in the XML document can also be returned

using several path using | character

E.g. Selects all the NAME elements of the EMPLOYEE element ofthe PAYROLL element AND all the BASICPAY elements in the

document

Path Expression: /PAYROLL/EMPLOYEE/NAME | //BASICPAY


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XPATH Axes

It is used to define a node set relative to the current node

Some of the axes are as:

AxisName Result

Ancestor Selects all ancestors (parent, grandparent, etc.) of the current node

ancestor-or-self Selects all ancestors (parent, grandparent, etc.) of the current node and the

current node itself

Attribute Selects all attributes of the current node

Child Selects all children of the current node

Descendant Selects all descendants (children, grandchildren, etc.) of the current node

descendant-or-self Selects all descendants (children, grandchildren, etc.) of the current node and the

current node itself

Following Selects everything in the document after the closing tag of the current node

following-sibling Selects all siblings after the current node

Namespace Selects all namespace nodes of the current nodeParent Selects the parent of the current node

Preceding Selects everything in the document that is before the start tag of the current node

preceding-sibling Selects all siblings before the current node

Self Selects the current node


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Location Path Expression

A location path can be absolute or relative.

An absolute location path starts with a slash ( / ) and arelative location path does not. In both cases the locationpath consists of one or more steps, each separated by aslash:

An absolute location path:

/step/step/...

A relative location path:

step/step/...


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Location Path Expression Syntax

The syntax for a location step is:

axisname::nodetest[predicate]

e.g Selects all EMPLOYEE nodes that are children of the current node

LPE: child::EMPLOYEE

e.g Selects all EMPLOYEE ancestors of the current node - and the

current as well if it is a EMPLOYEE node

LPE: ancestor-or-self::EMPLOYEE


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XPATH Operators

Returns either a node-set, a string, a Boolean, or a number.

Some Operators are:

|,+,-,div,=,,=,or, and, mod etc.


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XPATH implementation

/PAYROLL/EMPLOYEE/NAME

This XPATH expression needs to be embedded in HTML code asbelow

function loadXMLDoc(dname) { if (window.XMLHttpRequest) { xhttp=new XMLHttpRequest(); } else { xhttp=new ActiveXObject("Microsoft.XMLHTTP"); } xhttp.open("GET",dname,false); xhttp.send(""); return xhttp.responseXML; }


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xml=loadXMLDoc(emp.xml"); path="/PAYROLL/EMPLOYEE/NAME"

// code for IE if (window.ActiveXObject) { var nodes=xml.selectNodes(path); for (i=0;i


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SelfStudy

Go through XPATH functions


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XQUERY

The logic is similar to the query languages that we use inSQL for the database.

XQUERY is used to query to XML data from the XML

documents

XQuery is built on XPath expressions

XQuery and XPath share the same data model andsupport the same functions and operators


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Use ofXQUERY

Extract information to use in a Web Service

Generate summary reports

Transform XML data to XHTML

Search Web documents for relevantinformation


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We ll be referring to the same example emp.xml

Doc() function used by XQUERY to extract data from theXML documents alongwith the path expressions.

doc(emp.xml) /PAYROLL/EMPLOYEE/NAME

The resultant of XQUERY ll be

Leonardo Nasimeto


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Use of Predicates in XQUERY

doc(emp.xml") /PAYROLL/EMPLOYEE[BASICPAY>25000]

Where [BASICPAY>25000]is the Predicate

Resultant ll be

1011

>Leonardo Nasimeta

IT

30000

Pedro Almeida


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XQUERY FLWOR Expressions

FLWOR stands for For,Let, Where,Order By, Return

Path Expression:

doc(emp.xml") /PAYROLL/EMPLOYEE[BASICPAY>25000]/NAME

The corresponding FLWOR expression ll be

for $x in doc(emp.xml")/PAYROLL/EMPLOYEE

where $x/BASICPAY>25000

return $x/NAME

XQUERY resultant ll be


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Embedding it in HTML

{for $x in doc(emp.xml")/PAYROLL/EMPLOYEE/NAMEorder by $xreturn {$x}}

The resultant ll be

Leonardo Nasimeto


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Or to show data

{for $x in doc(emp.xml")/PAYROLL/EMPLOYEE/NAMEorder by $xreturn {data($x)}}

The resultant ll be

Juliana DantasLeonardo Nasimeto


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XQUERY conditional expressions

Like If-then-Else expressions

for $x in doc(emp.xml")/PAYROLL/EMPLOYEE/NAMEreturn if ($x/@status=contractual")then {data($x/NAME)}else {data($x/NAME)}

Adding text

Employee Details

{for $x in doc(emp.xml")/PAYROLL/EMPLOYEEorder by $x/NAMEreturn {data($x/NAME)}. Category: {data($x/@status}}


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Some XQUERY functions

let $name := (substring($NAME,1,4))

Note: Explore for other XQUERY functions

User defined XQUERY functions

Syntax:

declare functionprefix:function_name($parameterAS datatype)AS returnDatatype{...function code here...}


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XSCHEMA

It is a document that describes the structure

of the XML document related to elements thatcan appear in the document, about the orderof the elements etc.


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Definitions defined by XSCHEMA

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 includetext

defines data types for elements and attributes defines default and fixed values for elements and

attributes


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XSCHEMA Elements

Simple Element:The element that contains only text and do not contain anyother sub elements and attributes

syntax:

Complex Element:The element the contains other elements and attributes


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XSCHEMA Data Types

Some Data Types of XSCHEMA that arecommonly used:

xs:string xs:decimal

xs:integer

xs:boolean

xs:date

xs:time


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XSCHEMA Indicators

Indicators are used to control the usage of XML documents

Three categories and Seven Indicators

Order indicators: Defines the order of the elementsAllChoiceSequence

Occurrence indicators: Defines the number of usage of elementsmaxOccurs

minOccurs

Group indicators: Defines related sets of elementsGroup nameattributeGroup name


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Sequence Indicator: Specifies that the child elements must appearin a specific order

maxOccurs Indicator:specifies the maximum number of times anelement can occur


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minOccurs Indicator:Specifies the minimum number of times anelement can occur

Groupname:Element groups are defined with the group declaration


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Attribute GroupName: Attribute groups are defined within this


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John SmithOla NordmannLanggt 234000 StavangerNorway

Empire BurlesqueSpecial Edition110.90

Hide your heart

19.90

Example XML


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Example XSLSchema


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Browser Architecture

Web Browser Architecture


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Browser Architecture (Contd)

It comprises eight major subsystems plus the dependencies between

them:

(1) The User Interface subsystem is the layer between the user andthe Browser Engine. It provides features such as toolbars, visualpage-load progress, smart download handling, preferences, and

printing. It may be integrated with the desktop environment toprovide browser session management or communication with otherdesktop applications.

(2) The Browser Engine subsystem is an embeddable component that

provides a high-level interface to the Rendering Engine. It loads a

given URI and supports primitive browsing actions such as forward,

back, and reload. It provides hooks for viewing various aspects of

the browsing session such as current page load progress and

JavaScript alerts. It also allows the querying and manipulation of

Rendering Engine settings.

B A hit t (C td )


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Browser Architecture (Contd..)(3) The Rendering Engine subsystem produces a visual

representation for a given URI. It is capable of displaying HTML and

Extensible Markup Language (XML) (Bray et al., 2004) documents,optionally styled with CSS, as well as embedded content such asimages. It calculates the exact page layout and may use reflowalgorithms to incrementally adjust the position of elements on thepage. This subsystem also includes the HTML parser.

(4) The Networking subsystem implements file transfer protocols suchas HTTP and FTP. It translates between different character sets,and resolves MIME media types for files. It may implement a cacheof recently retrieved resources.

(5) The JavaScript Interpreter evaluates JavaScript (also known asECMAScript) code, which may be embedded in web pages.JavaScript is an object-oriented scripting language developed byNetscape. Certain Java-Script functionality, such as the opening ofpop-up windows, may be disabled by the Browser Engine orRendering Engine for security purposes.


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Browser Architecture (Contd..)

(6) The XML Parsersubsystem parses XML documents into a

Document Object Model (DOM) tree. This is one of the mostreusable subsystems in the architecture. In fact, almost all browserimplementations leverage an existing XML Parser rather thancreating their own from scratch.

(7) The Display Backend subsystem provides drawing and windowingprimitives, a set of user interface widgets, and a set of fonts. It maybe tied closely with the operating system.

(8) The Data Persistence subsystem stores various data associatedwith the browsing session on disk. This may be high-level data such

as bookmarks or toolbar settings, or it may be low-level data such ascookies, security certificates, or cache.


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Documents

Web Tech Class 7