Xml Notes

POTHURAI

Xml: - Extensible markup language. It is a Meta language. Meta language is a mother language of all other languages. Xml has no predefined elements & tags. So we must define our own tags. We can store limit amount of data. Xml documents are defined as .xml extension.

Xml is mainly useful to store, carry & exchange data, but it is not designed to display data.Note: - xml is language neutral, software, hardware independent tool for transmitting data.

Xml documents can also be used to store data in files or databases but some applications (xml parser, xml beans) can be written to store data & retrieve data from database.

Xml syntax rules: - The syntax rules of xml are very simple & strict. So creating that can read & manipulate xml is very easy.à All xml elements must have a closing tag with xml.Ex: - <p> this is a paragraph </p> //valid

<p> --------- // invalid in xml (it illegal to omit the closing tag)à Xml tags are case sensitive:

Opening & closing tags must be written with the same caseEx: - <Letter> tag is different from the tag <letter>à All elements must be properly nested. Improper nesting of tags makes no sense to xml. In xml all elements must be properly nested within each other like thisEx: - <b> <i> </i> </b> // valid

<b> <i> </b> </i> // invalidà All xml documents must have root element (parent element). All xml documents must contain a single tag pair to define a root element. All other element must be within this root element.Ex: - <root>

<child><sub child> ------- </sub child></child></root>

à Within xml, white space is preserved (continued). So, the white space in xml documented is not truncated.Element naming: - Xml elements must follow these naming rules (while defining own tags)

1) Names can contain letters, numbers & other characters.2) Names must not start with a number or punctuation character.3) Names must not start with the letters (xml or Xml or XML…).4) Names can not contain spaces

<message> -------- </message> // valid<\mess> ------- </mess> // invalid<first mess> ------- </first mess> // invalid

SUDHEER REDDY

1

POTHURAI

à Attributes values must always be quoted with xml, it is illegal to omit quotation marks around attribute values. Xml elements can have attribute in name / value pairs just like html.

<day date=”12/11/2008”>This is correct: “12/11/2008”This is in correct: 12/11/2008à <? xml version=”1.0” encoding=”ISO-8859-1”?>

æ æCompulsory not compulsory

This is the 1st element of every xml program.

Program: - <?xml version="1.0"?><student age="25"> <sname> Sudheer Reddy </sname> <sid> 630130 </sid> <course> Java package </course> <address> <stname> Ram Nagar </stname> <city> ATP </city> <state> AP </state> </address></student>

Xss: - xml style sheets.Dtd: - document type definition.Css: - cascading style sheets.Xsl=xml document + css commands.DHTML page=html page+ JavaScript code+ css commands.

Program: - <?xml version="1.0"?><book><title> HTML black book </title><author> Sudheer </author><price> 450.94 </price><prod id="3454" media="paper"> </prod><chapter>Introduction to html<topic> html basic Structure </topic><topic> html tags </topic><topic> html table </topic></chapter><chapter>Introduction to xml<topic> Xml Syntax rules </topic><topic> Xml validation </topic>

SUDHEER REDDY

2

POTHURAI

</chapter></book>

Xml validations: - Well formed xml document is a xml document that confirms to syntax rules of xml. Valid xml must be well form document & also confirms to syntax rules of either xml DTD or xml Schema facility.Xml DTD: - xml DTD is the old facility that validates xml documents. DTD defines document structure with list of (legal) elements & their data types to store. The purpose of DTD is defining components of xml documents. It represents a group of elements. DTD can be declared inline in xml documents or as external references.Internal DTD: - It DTD structure is included in xml documents; It should be wrapped or embedded in DOCTYPE declaration as shown below

<! DOCTYPE rootele [declare] >External DTD: - It DTD is external to xml document; it should be wrapped (placed) within DOCTYPE declaration as shown below

<! DOCTYPE rootele SYSTEM”.dtd”>Declaring root element: - Element with one or more child elements is declared with element declaration as shown below

<! ELEMENT rootele (child)> (or)<! ELEMENT rootele (child1,child2,child3,-------)>

Ex: - <! ELEMENT letter (to,from,message)>Declaring child element: - Element with simple content is declared by element declaration as shown below

<! ELEMENT childele (data type)><! ELEMENT to(#PCDATA)><! ELEMENT from(#PCDATA)><! ELEMENT message(#PCDATA)>

à Data types are 2 types1) PCDATA parsed character data2) CDATA character data

All elements are declared in PCDATA. All attributes are declared in CDATA. Converting 1 data type into another data type is called parse.PCDATA it represents the text that found between begin tag & end tag of element. But the text parsed by a parser. Generally we can dell are child elements with PCDATA.CDATA it also represents the text but that will not parsed by a parser.Note: - using CADTA attributes cam be declared attributes.

Internal DTD Ex: - <?xml version="1.0"?><!DOCTYPE student [<!ELEMENT student (#PCDATA)><!ELEMENT sname (#PCDATA)><!ELEMENT sid (#PCDATA)><!ELEMENT course (#PCDATA)><!ELEMENT address (#PCDATA)><!ELEMENT stname (#PCDATA)>

SUDHEER REDDY

3

POTHURAI

<!ELEMENT city (#PCDATA)><!ELEMENT state (#PCDATA)>]><Student> <sname> Sudheer Reddy </sname> <sid> 630130 </sid> <course> java package </course> <address> <stname> Ram Nagar </stname> <city> ATP </city> <state> AP </state> </address></Student>

(Or)<!ELEMENT student (#PCDATA)><!ELEMENT sname (#PCDATA)><!ELEMENT sid (#PCDATA)><!ELEMENT course (#PCDATA)><!ELEMENT address (#PCDATA)><!ELEMENT stname (#PCDATA)><!ELEMENT city (#PCDATA)><!ELEMENT state (#PCDATA)>

Save: - Student form.dtd

External DTD Ex: - <?xml version="1.0"?><!DOCTYPE student SYSTEM "D:\Student form.dtd "><Student> <sname> Sudheer Reddy </sname> <sid> 630130 </sid> <course> java package </course> <address> <stname> Ram Nagar </stname> <city> ATP </city> <state> AP </state> </address></Student>

à DTD provides 3 Symbols 1) + ---- 2) * ----- 3)? -----+=One or more occurrence*=0 or more occurrence?=0 or one occurrenceEx: -

<! ELEMENT author (#PCDATA)>à Declaring one or more occurrence of same elements. <! ELEMENT letter (message +)>

SUDHEER REDDY

4

POTHURAI

<! ELEMENT message (#PCDATA)> In above example + sign defines that the message element must occur one or more times inside letter element.Xml doc:- <letter> <message> hai </message> <message> how r u </message> </letter><letter> </letter> //invalid à Declaring 0 or more occurrence of same line. Ex:- <! ELEMENT letter (message *)> <! ELEMENT message (#PCDATA)> In the above example & declares that the message element can occur 0 or more lines inside letter element. Ex: - <letter> </letter> //valid

<letter> <message> hai </message> <message> how r u </message> </letter>

à declaring 0 1 occurrence of element Ex:- <! ELEMENT letter (message?)> <! ELEMENT message (#PCDATA)>In the above example & declares that the message element can occur 0 or 1 time inside letter element. Ex: - <letter> </letter> //valid

<letter> <message> hai </message> </letter>// valid

<letter> <message> hai </message> <message> how r u </message> </letter> // invalid

Declaring elements with mixed elements: - We can declare element with mixed content (both text & child elements) by ELEMENT declaration as shown below<! ELEMENT elename (#PCDATA | eleneme1 | elename2|------)*>Ex: - <! ELEMENT chapter (#PCDATA | topic)*>Xml doc: - <chapter>

<topic> first topic </topic><topic> second topic </topic></chapter>

Declare element with empty content: - We can declare element with empty content by using keyword EMPTY as shown below

SUDHEER REDDY

5

POTHURAI

<! ELEMENT elename EMPTY>Ex: - <! ELEMENT prod EMPTY>Xml doc: - <prod> </prod> // valid

<prod> ---- </prod> // invalid

Declare attributes in DTS: - In DTD one or more attributes are declare with ATTLIST declaration as shown below

<! ATTLIST elename attrname attrtype attrvalue>Attrvalue description

1) Default default value 2) #REQUIRED attrvalue must be included 3) #IMPLID attrvalue doesn’t have to be included 4) #FIXED attrvalue is fixed or constant

1) default: -Ex: - <! ELEMENT company EMPTY>

<! ELEMENT company cname CDATA “Micro soft”>Xml doc: - <company cname=”Micro soft”> </company> // valid

<company cname=”Sudheer”> </company> // valid2) #REQUIRED: - Ex: - <! ELEMENT company EMPTY>

<! ELEMENT company cname CDATA “#REQUIRED”>Xml doc: - <company> </company> // invalid

<company cname=”Sudheer”> </company> // valid3) #IMPLID: - Ex: - <! ELEMENT company EMPTY>

<! ELEMENT company cname CDATA “#IMPLID”>Xml doc: - <company> </company> // valid

<company cname=”Sudheer”> </company> // valid4) #FIXED: -Ex: - <! ELEMENT company EMPTY>

<! ELEMENT company cname CDATA “#FIXED”>Xml doc: - <company cname=”Micro soft”> </company> // valid

<company cname=”Sudheer”> </company> // valid

Declaring entities: - Entities are names, use to define short cut for same common text. In DTD entities are declare with ENTITY declaration as shown below

<! ELEMENT author (#PCDATA)><! ENTITY entityname “common text”>

Create a DTD file: - Open xml spy softwareXml spyà file à new à dtd à Click ok

Program: - <?xml version="1.0" encoding="UTF-8"?> // is the default statement of

document type definition.<!ELEMENT bookinfo (book+)><!ELEMENT book (title,author+, price,prod,chapter+)>

SUDHEER REDDY

6

POTHURAI

<!ELEMENT title (#PCDATA)><!ELEMENT author (#PCDATA)><!ELEMENT price (#PCDATA)><!ELEMENT prod EMPTY><!ELEMENT chapter (#PCDATA|topic)*><!ELEMENT topic (#PCDATA)><!ATTLIST prod id CDATA "#REQUIRED" media CDATA "#IMPLID"><!ENTITY cost "534.654">

Save: - booksinfo.dtd

File à new à Extensible Markup Language à dtd à ok à browse à booksinfo.dtd à click ok

Program: - <?xml version="1.0" encoding="UTF-8"?><!DOCTYPE bookinfo SYSTEM "D:\psr\Xml programs\ bookinfo.dtd" > // is the default statement of Extensible Markup Language<bookinfo>

<book><title> Computer Networks </title><author> SUDHEER </author><price> &cost ;</price><prod id="123" media=""></prod><chapter> introduction to network <topic> what is net work </topic> <topic> different types of network </topic> </chapter>

</book><book>

<title> layers </title><author> Sunil </author><price> &cost; </price><prod id="321" media=" "></prod><chapter> introduction to layers <topic> what is layer </topic> <topic> different types of layers </topic> </chapter>

</book></bookinfo>

Save: - bookinfo.xml

DTD limitations: - 1) xml dtd doesn’t provide restrictions (freshets) on data, because it has no primitive data types.2) DTD doesn’t support name space.

SUDHEER REDDY

7

POTHURAI

Name space: - name space provides methods to avoid elements name comfit (comfit means confusion). Since elements names are not predefined in xml, element name comfit will occur when two different documents have same element names.Ex: - <table>

<td> mango </td><td> orange </td><td> grapes </td>

</table>------------------------------------<table>

<name> heritage </name><color> brown </color><price> 232 </price><size> 453 </size>

</table>

à Here both documents are having same root element. So there will be element name comfit occur.

When above 2 documents are combined there will be element have comfit, because both documents have same element name.

à Avoid element name comfit using prefix notation.Ex: - <f:table>

< f:td> mango </ f:td>< f:td> orange </ f:td>< f:td> grapes </ f:td>

</ f:table>------------------------------------<g:table>

< g:name> heritage </ g:name>< g:color> brown </ g:color>< g:price> 232 </ g:price>< g:size> 453 </ g:size>

</ g:table>Avoid element name comfit using name space. For this they invented one attribute called attributes xmlns, to give meaningful name of xml document.Syntax: - xmlns:prefix=”URI/URL”

æ æ Attribute name attribute value.Ex: - <f:table xmlns:f=”Sunil.table.fruits”>

<f:td> grapes </f:td><f:td> mango </f:td>

</f:table> Xmlns=” “ à It has default prefix. It is used to no declare the prefix in the child tags.

SUDHEER REDDY

8

POTHURAI

Xml schema: - It is newly defined facility that validates xml documents.Xml schema is based alternative to DTD facility. It is recommended by W3C people. Just like DTD, xml schema also provides documents structure with the list of legal elements. Xml schema documents are referred to as .xsd extension.

It provides group of primitive data types (int, float, double, String, char, date, time, etc ...). It supports name spaces. We can identify the extension is xs: predefined data type.

These are the features of the xml schema.

Creating xml scheme: - Xml spyà file à new à xsd à Click ok

"ENTER_NAME_OF_ROOT_ELEMENT_HERE" is the default root name.Click the element & enter the root name.

Root name à right click à add child à select sequence Sequence à right click à add child à select element

Enter element name & select the type=xs: string in details bar.Sequence à right click à add child à select element

Enter element name & select the type=xs: int in details bar.Sequence à right click à add child à select element

Enter element name & select the type=xs: long in details bar.Element à right click à add child à select sequence Sequence à right click à add child à select element

Enter element name & select the type=xs: string in details bar.

Schema design à schema setting à click

& click ok button.Save: - emp.xsd

SUDHEER REDDY

9

POTHURAI

File à new à Extensible Markup Language à schema à ok à browse à emp.xsd à click ok

<?xml version="1.0" encoding="UTF-8"?><emp xmlns="sunil.info.emp" xmlns:xsi= "http://www.w3.org/ 2001/ XMLSchema-instance" xsi:schemaLocation="sunil.info.empD:\psr\XMLPRO~1\emp.xsd">

<ename> Sunil </ename><eid> 1 </eid><sal> 20000 </sal><address>

<street> Rahamat Nagar </street><city> HYD</city><state> AP </state><phno> 9290198907 </phno>

</address></emp>

Save: - emp.xml

Code: - <?xml version="1.0" encoding="UTF-8"?><xs:schema targetNamespace="sunil.info.emp" elementFormDefault= "qualified" attributeFormDefault="unqualified" xmlns= "sunil.info.emp" xmlns:xs=" http://www.w3.org/2001/XMLSchema">

<xs:element name="emp"><xs:annotation>

<xs:documentation>Comment describing your root element </xs:documentation>

</xs:annotation><xs:complexType>

<xs:sequence><xs:element name="ename" type="xs:string"/>

<xs:element name="eid" type="xs:int"/><xs:element name="sal" type="xs:float"/>

<xs:element name="address"><xs:complexType>

<xs:sequence><xs:element name="street" type="xs:string"/>

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

<xs:element name="state" type="xs:string"/>

SUDHEER REDDY

10

POTHURAI

<xs:element name="phno" type="xs:long"/>

</xs:sequence></xs:complexType>

</xs:element></xs:sequence>

</xs:complexType></xs:element>

</xs:schema>

Xml spyà file à new à xsd à Click ok

Schema design à schema setting à click

& click ok button.

Save: - films.xsd

File à new à Extensible Markup Language à schema à ok à browse à films.xsd à click ok

<?xml version="1.0" encoding="UTF-8"?><filmsinfo xmlns="latha.films.info" xmlns:xsi="http://www.w3.org/ 2001/XMLSchema-instance" xsi:schemaLocation="latha.films.info

SUDHEER REDDY

11

POTHURAI

D:\psr\XMLPRO~1\filmsinfo.xsd"><movies>

<title> Yama Donga </title><hero> N.T.R</hero><heroein> Priya Mani </heroein><vilan> Jaya Prakash Reddy </vilan><directer> Rajamouli </directer><producer> xxx </producer><artists> xxxx </artists>

</movies><movies>

<title> Sivaji </title><hero> Rajani </hero><heroein> Shriya </heroein><vilan> xxx </vilan><directer> Sankar </directer><producer> B Suresh </producer><artists> xxxx </artists>

</movies></filmsinfo>

Save: - films.xml

SUDHEER REDDY

12

Xml Notes

Documents

Transcript of Xml Notes