distributed system for lab session

1. XML

2. Agenda
At the end of this presentation, you will be able to understand :
Understand why we need XML
Understand the features of XML
 Create and use XML files
Understand and use DTDs
Understand XSD and XPath
Use XML parsers like SAX and DOM parser
 Create and use XSL files

3. John works on a project

4. John Suggests the ways!

5. John Collects Data..
The organization has many departments like HR, Admin, R&D, Marketing, Sales, Technical
Writing etc., Mark gets data from all departments in a different format. Mark is unable to
read the files from the program as the format from each department is different.

6. Data in XML format

7. Mark has a doubt..

8. John explains XML

9. John explains XML
Lets study XML
deeply

10. Features of XML
Simplicity - Writing XML is very easy.
Extensibility - XML data can be extended with DTD and XSL. DTD is Document Type
definition which provides the format of the XML document and XSL is the way XML data will
be represented/displayed. It is like CSS for HTML.
Interoperability - It can work on any platform.
Openness - Any tool/language can open an xml file and parse it in the programming
language.

11. XML
Data is inserted in the XML file in tags like HTML.
XML is written using user defined tags and data is written in
between the user defined tags.
User can open the xml file in any text editor or xml editors.
 It can also read/parsed using computer languages.

12. What does XML consist of?

13. Where can we use XML?
XML can be used to:
Exchange data between different systems
Share data
Store data
Make data in more useful and meaningful form
create new “ML Languages”

14. Is there a difference between XML and HTML?

15. John explains the Difference

16. Difference between HTML and XML

17. Simple XML File
XML file will have an extension of .xml for the file name.
When you double click on XML file, it can be opened in any browser.
Sample XML file is given below:
<person>
<name> Berhanu</name>
<class> Java </class>
<profession> Trainer </profession>
<location> Adama </location>
</person>

18. Simple XML File
Here <person>,<name>,<class>, <profession> and <address> are
tags.
Data will be written in between these tags.

19. XML as Tree
 XML forms a tree structure. Here root_e|ement is the root of the tree, person is a branch and name, class, profession
and location are the leaves of the tree.
<root_element>
<person>
<name> Emnet </name>
<class> Java </c1ass>
<profession> scholar</profession>
<1ocation> Adama</location>
</person>
<person>
<name> Mituku</name>
<class> Java </class>
<profession> Software developer </profession>
<location> California </location>
</person>
</root_e1ement>

20. XML Rules
White spaces are ignored in HTML but XML considers white spaces as the
actual data.
Ordering and nesting of XML document should be proper. XML file does not
work properly if there is clash in nesting.
XML tags are case sensitive. Opening and closing tags should be exactly the
same without any difference in the case.
Every opening tag must have a close tag else XML file will not work correctly.

21. XML Namespace

22. XML NameSpace

23. XML Name Space
Syntax of Name space is:
Element:name space xmlns:name space=”name space identifier”

24. XML Prolog
First line of XML is called Prolog.
Prolog will contain the following:
<?xm| version="1.0" encoding="UTF-8"?>
Prolog usually have version number and encoding.
Encoding is like character set. This is used for Unicode.
UTF stands for Universal character set Transformation Format.
UTF-8 is used for standard web applications.

25. Editing and Viewing the XML Files

26. XML DTD
DTD stands for Document Type Definition.
DTD specifies the format of the XML Document.
DTD can be inside an XML file or outside the XML file.

27. Document Type Definitions
 Provide way to constrain XML document content
 Specify what kind of content can appear and where
 Relatively simple to write, but not powerful
 Markup declarations that define document content
DTD specify the following
 Elements
 Attributes
 Entities
 Processing instructions
 Comments
 Parameter entity references
DTD Format:
<!DOCTYPE Name [
Document Type Definition
]>

28. Declaring Elements in DTD
<!ELEMENT Name ContentSpecification>
 EMPTY content- element has no child elements
 ANY content – element has no content constraints
 Element content – can contain specified elements
 Mixed Content – can contain elements and character data
Eg:
<!ELEMENT MISCELLANEOUS ANY>
<!ELEMENT IMG EMPTY>
<!ELEMENT NAME (#PCDATA)>
<!ELEMENT CD (TITLE, ARTIST)>
<!ELEMENT DWELLING (HOUSE |ROOM | CONDOMINIUM| TRAILER)>
<!ELEMENT TITLE (#PCDATA | SUBTITLE )>
Specifying element population limits:
? Means zero or one of the element
+ means one or more of the element
• Means zero or more of element
Eg:
<!ELEMENT LETTER (A?, B*,C+)>

29. Declaring Attributes in DTD
 All attributes must be declared
Format:
<!ATTLIST ElementName AttrName Type DefaultDecl >
String: indicated by CDATA
Enumerated: can be one of a list of values
Tokenized: used for IDs, other advanced DTD features
Eg:
<! ATTLIST PACKAGE status CDATA “OK”>
<! ATTLIST DWELLING type (house |condominium | tailer) >
Default Attributes:
#REQUIRED: attribute must be present
#IMPLIED: attribute is optional
Default value: value to use for default
#FIXED: fixed at certain value
Eg:
<ATTLIST PACKAGE ontime (yes| no) #REQUIRED)
<ATTLIST PACKAGE ontime (yes| no) #IMPLIED)
<ATTLIST PACKAGE ontime CDATA #FIXED “yes”)

30. DTD
1 <?xml version=“1.0” encoding=“UTF-8”?>
2 <!DOCTYPE TEST SYSTEM “Test.dtd”>
3 <TEST>
4 <Name> Berhanu</Name>
5 <From>Adama</From>
6 <Profession> Teaching</Profession>
7 </TEST>
8
9 Content of the file: Test.dtd
10 <!DOCTYPE TEST>
11 [
12 <!ELEMENT TEST (Name,From,Profession)>
13 <!ELEMENT Name (#PCDATA)>
14 <!ELEMENT From (#PCDATA)>
15 <!ELEMENT Profession (#PCDATA)>
16 ]>

31. DTD
DOCTYPE says the root element of the XML file.
ELEMENT Test says it has 3 elements which are Name, from and Profession.
All the ELEMENTS are PCDATA, that means all the elements are parsable
character data.
At times you need not parse certain elements then you can use CDATA.
Using XML parser, using validate() we can validate XML whether it is formed
according to DTD or not.

32. Why DTD?
Even the XML file can be written in different formats by different people.
To avoid this issue and to standardize the XML data in one format, DTD is
helpful and useful.

33. Features of DTD
Providing standard way of representing data.
XML data can be validated with DTD.
DTD can be given in the xml file or it can be given in a separate file having
extension of .dtd and can use it in the XML file.
During the validation of XML, parsers read the DTD file and validates against
the XML file. Finally validator will give the result as valid XML or Invalid XML.

34. XPath
 XPath is a language for addressing
parts of an XML document, designed to
be used by both XSLT(XSL5
Transformations) and XPointer to
provide a common syntax and
semantics for functionality shared
between them.
The primary purpose of XPath is to
address parts of an XML [XML]
document. In support of this primary
purpose, it also provides basic facilities
for manipulation of strings, numbers
and booleans.

35. XSD(XML Schema Definition)
An XML schema represents the
interrelationship between the
attributes and elements of an XML
object (for example, a document or a
portion of a document).
 This description can be used to
verify that each item of the content in
a document adheres to the
description of the element in which
the content used to be placed.
To create a schema for a document,
you analyze its structure, defining
each structural elements as you
encounter it.

36. XSD(XML Schema Definition)
Alternative way of specifying rules to DTDs
Provide way to constrain XML document content
Written using XML syntax
Similar to DTDs, but more powerful and sophisticated
 Finer level of control than DTDs allow
 Schema and XML files always stored separately

37. Anatomy of a Schema
 Uses namespace http://www.w3.org/2001/XMLSchema
 Usually uses the “xsd” prefix
<xsd:schema xmlns:xsd="http://www.w3.0rg/2001/XMLSchema”>
<xsd:element name="ElemName”>
<!-- other content definitions go in here -->
<xsd:attribute name="AttrName”/>
</xsd:element>
</xsd:schema>

38. Declaring Elements in Schema
 Declared using <xsd:element> tag
 Can be declared as either simple or complex type
Elements can have mixed or empty element content
Elements can have min and max times they can occur
Elements can be restricted to having certain values

39. Simple Schema Types

40. Simple Schema Types

41. Declaring Elements in Schema
 <xsd:element name="MyElement” type="xsd:string”>
 <xsd:elment name="HireDate” type="xsd:date”>
 <xsd: elment name="Friends” type="xsd:string”
minoccurs="1” maxoccurs="unbounded”>
 <xsd:element name="Phone” type="xsd:string” maxoccurs="5">

42. Declaring Elements in Schema
 Can declare custom types, derived from existing types
<xsd:element name="InvitedGuests”>
<xsd:simpleType>
<xsd:restriction base="xsd:positiveInteger”>
<xsd:minInclusive value="0">
<xsd:maxInclusive value="50">
</xsd:restriction>
</xsd:simpleType>
</xsd:element>
Eg of XML:
< InvitedGuests> 0 to 50</ InvitedGuests>

43. Declaring Elements in Schema
Can restrict content to a range of choices
<xsd:element name="dwelling”>
<xsd:simpleType>
<xsd:restriction base="xsd:string”>
<xsd:enumeration value="house”>
<xsd:enumeration value="apartment”>
<xsd:enumeration value="trailer”>
</xsd:restriction>
</xsd:simpleType>
</xsd:element>
Eg of XML:
< dwelling > house/ apartment / trailer </ dwelling >

44. Declaring Elements in Schema
 Restrictions can even use regular expression patterns
<xsd:element name="SSN”>
<xsd:simpleType>
<xsd:restriction base="xsd:string”>
<xsd:pattern value="d{3]-d{2}-d{4}">
</xsd:restriction>
</xsd:simpleType>
</xsd:element>
Eg of XML:
< SSN >123-45-6789</ SSN >

45. Declaring Complex Types
 Use the xsd:anyType value for the type attribute
 Use the <xsd: complexType> tag in the definition
<xsd:element name="EmptyElem”>
<xsd:complexType>
</xsd:complexType>
</xsd:element>
Eg of XML:
< EmptyElem ></ EmptyElem>

46. Declaring Complex Types
 Declaring elements with mixed content
<xsd:element name="title”>
<xsd:complexType mixed="true”>
<xsd:sequence>
<xsd:element name="subtitle”>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
Eg of XML:
< title>
< subtitle> </ subtitle>
</ title >

47. Declaring Complex Types
 Declaring elements with element content
<xsd:element name="address”>
<xsd:complexType>
<xsd:sequence>
<xsd:element name="num” type="xsd:integer”/>
<xsd:element name="street” type="xsd:string”/>
<xsd:element name="city” type="xsd:string”/>
<xsd:element name="state” type="xsd:string”/>
</xsd: sequence>
</xsd:complexType>
</xsd:element>
Eg of XML:
< address >
< num >123 </num>
< street > abc</ street >
< city >Adama </ city >
< state > Oromia</ state >
</ address >

48. Declaring Complex Types
 Declaring elements with element content
<xsd:element name="vehicle”>
<xsd:complexType>
<xsd:choice>
<xsd:element name="car” type="xsd:string”/>
<xsd:element name="bus” type="xsd:string”/>
<xsd:element name="van” type="xsd:string”/>
<xsd:element name="truck” type="xsd:string”/>
</xsd:choice>
</xsd:complexType>
</xsd:element>
Eg of XML:
< vehicle >
< car >Yaris </ car > or
< bus > tata</ bus > or
< van >hilex </ van > or
< truck > mahindra</ truck >
</ vehicle >

49. Declaring Complex Types
 Declaring elements with element content
<xsd:element name="CapitalCity”>
<xsd:complexType>
<xsd:all>
<xsd:element name="name” type="xsd:string”/>
<xsd:element name="state” type="xsd:string”/>
<xsd:element name="pop” type="xsd:positiveInteger”/>
</xsd:all>
</xsd:complexType>
</xsd:element>
Eg of XML: any order
< CapitalCity >
< name >berhanu </ name >
< state > oromia</ state >
< pop >12333 </ pop >
</ CapitalCity >

50. Declaring Attributes in Schema
 Declared using <xsd:attribute> tag
Are always declared as simple types
 Can use any of the types used by elements.
<xsd:attribute name="age” type="xsd:integer”>
<xsd:attribute name="age” type="xsd:integer” use="optional”>
(The “use” attribute can also be “required” or “prohibited”)
<xsd:attribute name="age” type="xsd:integer” default="20">

51. Declaring Attributes in Schema
Adding attribute to element that has character data
<xsd:element name="Name”>
<xsd:complexType mixed="true”>
<xsd:attribute name="Age” type="xsd:integer”>
</xsd:complexType>
</xsd:element>
Eg of XML:
< Name Age =“35”> </ Name >

52. Declaring Attributes in Schema
 Adding attribute to element that has empty content
<xsd:element name="Image”>
<xsd:complexType>
<xsd:attribute name="src” type="xsd:string”>
</xsd:complexType>
</xsd:element>

53. Declaring Attributes in Schema
 Adding attributes to element that has mixed content
<xsd:element name="car”>
<xsd:complexType>
<xsd:sequence>
<xsd:element name="make” type="xsd:string”>
<xsd:element name="model” type="xsd:string”>
</xsd:sequence>
<xsd:attribute name="year” type="xsd:gYear”>
</xsd: complexType>
</xsd:element>

54. XSD for Business card XML
<?xml version="1.0" encoding="utf-8" ?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<xsd:element name="BusinessCard">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Name" type="xsd:string"/>
<xsd:element name="phone" maxOccurs="unbounded">
<xsd:complexType mixed="true">
<xsd:attribute name="type" use="required">
<xsd:simpleType>
<xsd:restriction base="xsd:string">
<xsd:enumeration value="mobile"/>
<xsd:enumeration value=”work"/>
<xsd:enumeration value=”home"/>
<xsd:enumeration value=”fax"/>
</xsd:restriction>
</xsd:simpleType>
</xsd:attribute>
</xsd:complexType>
</xsd:element>
<xsd:element name="email" type="xsd:string" minOccurs="0" />
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:schema>
Businesscard XML:
<?xml version="1.0" encoding="utf-8" ?>
<BusinessCard>
<Name>Abebe</Name>
<phone type="mobile">(251) 9621-03206</phone>
<phone type="work">(251) 9621-03207</phone>
<phone type=”home">(251) 9621-4444</phone>
<phone type="fax">(251) 9621-1234</phone>
<email>abebesoft@astu.edu</email>
</BusinessCard>

55. XML Parsers

56. Difference between DOM and SAX Parsers

57. Why DOM and SAX?
From the program, if the xml file data is to be read then developer has to
write their own code to parse the xml file. It is complicated.
To avoid this, Java/programming language has given parsers like DOM and
SAX to read the xml file.
XML parser consumes lot of time and it is complicated, DOM/SAX parser is
used to parse the xml file. Using this, the code can be developed fast and
accurate.

58. Features of DOM and SAX?
DOM reads the XML file and stores in tree format.
 SAX reads in event based format.

59. DOM parsing - creating XML file using DOM - Required Import
import javax.xml.parsers.*;
import org.w3c.dom.*;
import java.io.*;
import javax.xml.transform.*;
import javax.xml.transform.dom.*;
import javax.xml.transform.stream.*;

60. DOM to Create XML file

61. DOM to Create XML file
In the program, document object is created.
Elements/nodes of the XML file are created.
Data to be placed in between the nodes, are created in text object.
Text and elements (nodes) are linked.
Nodes are linked to the Root node.
Finally, transformer Transform() method is used to convert the document object to XML file.

62. Parsing XML file using DOM-Required Imports

63. Parsing XML file using DOM

64. SAX Parser – Required Imports

65. SAX Parser
In the main () method, XML file is parsed by SAXParser object and is attached with a
mySaxHandler class.
For every node or data read, it calls a corresponding method in mysaxHandler class.
StartDocument() and endDocument() methods are called when an XML document is started
to read and after reading the entire document.
When start tag is read, startEIement() method is invoked.
When end tag is read, end Element() method is invoked.
When the data in-between the tag is read, characters() method is called.

66. John works on a project

67. John works on a project

68. Why XSL?
XML is used only to store data.
We need a mechanism to display the data in a specified format. This
is possible using XSL.

69. What is XSL?
XSL stands for Extensible Stylesheet Language.
Like the way CSS is stylesheet for HTML, XSL is the stylesheet for
XML.
XSL can navigate all the nodes/elements of the XML file and can
display the XML data in the particular format. This is done by XSLT
which stands for Extensible stylesheet Language Transformations.

70. Features of XSL
 Representing the XML data in the required style.
 Queries also can be specified in XSL.
 XSL file reads the XML data, looks for the query (If it is given in the
XSL file) and displays the data on browser in the format given in the
XSL file.

71. XSL File
This line should be used in the XML file to use the XSL file.
This line will use the XML data and use XSL format and displays XHTML in the
browser.
Note: Browser should support XSLT, other wise the above code will not work.

72. Sample XML File
<?xml version="1 . O"?>
<?xml-stylesheet type="text/xsl” href="Welcome.xsl"?>
<Greet>
<by>a developer</by>
<greeting>Hello..</greeting>
</Greet>

73. Sample XSL File

74. XML file will display

75. Relationship between XML specifications