XML
- 2. Disadvantages of HTML – Need for XMLHTML lacks syntax checking
- 4. HTML is not suitable for data interchange
- 5. HTML is not context aware – HTML does not allow us to describe the information content or the semantics of the document
- 6. HTML is not object-oriented
- 7. HTML is not re-usable
- 8. HTML is not extensibleIntroduction to XMLXML – Extensible Markup Language
- 9. Extensible – capable of being extended
- 10. Markup – it is a way of adding information to the text indicating the logical components of a document
- 11. How is it different from HTML?
- 12. HTML was designed to display data
- 13. XML was designed to store, describe and transport data
- 14. XML is also a markup language like HTML
- 15. XML tags are not predefined – we must design our own tags.Differences between HTML and XML
- 16. Advantages (Features) of XML - 1XML simplifies data sharingSince XML data is stored in plain text format, data can be easily shared among different hardware and software platforms.XML separates data from HTMLTo display dynamic data in HTML, the code must be rewritten each time the data changes. With XML, data can be stored in separate files so that whenever the data changes it is automatically displayed correctly. We have to design the HTML for layout only once.
- 17. Advantages (Features) of XML - 2XML simplifies data transport
- 18. With XML, data can be easily exchanged between different platforms.
- 19. XML makes data more available
- 20. Since XML is independent of hardware, software and application, XML can make your data more available and useful.
- 21. Different applications can access your data in HTML pages
- 22. XML provides a means to package almost any type of information (binary, text, voice, video) for delivery to a receiving end.Advantages (Features) of XML - 3InternationalityHTML relies heavily on ASCII which makes using foreign characters very difficult. XML uses Unicode so that many European and Asian languages are also handled easily
- 23. Applications of XMLFile ConvertersMany applications have been written to convert existing documents into the XML standard. An example is a PDF to XML converter. Cell Phones - XML data is sent to some cell phones. This data is then formatted to display text or images, and even to play sounds!VoiceXML - Converts XML documents into an audio format so that you can listen to an XML document.
- 24. XML Document – Example 1<?xml version="1.0" encoding="ISO-8859-1"?><class_list><student><name>Anamika</name><grade>A+</grade></student><student><name>Veena</name><grade>B+</grade></student></class_list>
- 25. XML Document–Example 1 - ExplainedThe first line is the XML declaration.
- 27. It defines the XML version (1.0)
- 28. It gives the encoding used (ISO-8859-1 = Latin-1/West European character set)
- 29. The XML declaration is actually a processing instruction (PI) an it is identified by the ? At its start and end
- 30. The next line describes the root element of the document (like saying: "this document is a class_list“)
- 31. The next 2 lines describe 2 child elements of the root (student, name, and grade)
- 32. And finally the last line defines the end of the root element: </class_list>Logical StructureXML uses its start tags and end tags as containers.The start tag, the content and the end tag form an elementElements are the building blocks out of which an XML document is assembled.An XML document has a tree-like structure with the root element at the top and all the other elements are contained within each other.
- 33. Tree structureXML documents form a tree structure.
- 34. XML documents must contain a root element. This element is "the parent" of all other elements.
- 35. The elements in an XML document form a document tree. The tree starts at the root and branches to the lowest level of the tree.
- 36. All elements can have sub elements (child elements)
- 38. XML – Example 2<bookstore> <book category = "COOKING"> <title lang = "en">Everyday Italian</title> <author>Giada De Laurentiis</author> <year>2005</year> <price>30.00</price></book> <book category = "CHILDREN"> <title lang = "en">Harry Potter</title> <author>J K. Rowling</author> <year>2005</year> <price>29.99</price></book> <book category = "WEB"> <title lang = "en">Learning XML</title> <author>Erik T. Ray</author> <year>2003</year> <price>39.95</price></book></bookstore>
- 39. Important DefinitionsXML ElementAn element is a start tag, content, and an end tag.E.g., <greeting>”Hello World</greeting> XML AttributeAn attribute provides additional information about elementsE.g., <note priority = “high”>
- 40. Important DefinitionsChild elements – XML elements may have child elements<employee id = “100”> <name> <first>Anita</first> <initial>D</initial> <last>Singh</last> </name></employee>Parent Element NameChildren of parent element
- 41. XML ElementAn XML element is everything from the element's start tag to the element's end tag.An element can contain other elements, simple text or a mixture of both. Elements can also have attributes.
- 42. XML Syntax RulesAll XML elements must have a closing tagXML tags are case sensitive. The tag <Book> is different from the tag <book>Opening and closing tags must be written with the same case <Message>This is incorrect</message><message>This is correct</message>
- 43. XML Syntax RulesXML elements must be properly nested
- 44. HTML permits this:<B><I>This text is bold and italic</B></I> But in XML this is invalid. All elements must be properly nested within one another.<B><I>This text is bold and italic</I></B>XML documents must have a root element. It is the parent of all other elements.<root> <child> <subchild>.....</subchild></child></root>
- 45. XML Syntax RulesXML Entity ReferencesSome characters have a special meaning in XML. E.g., If you place a character like "<" inside an XML element, it will generate an error because the parser interprets it as the start of a new element.<message>if salary < 1000 then </message>To avoid this error, replace the "<" character with an entity reference:<message>if salary < 1000 then</message>
- 46. XML Syntax RulesXML Entity ReferencesThere are 5 predefined entity references in XML:
- 47. XML Syntax RulesComments in XML (similar to HTML) <!-- This is a comment --> White space is preserved in XML but not in HTML
- 48. XML Naming Rules
- 49. Names can contain letters, numbers, and other characters
- 50. Names cannot start with a number or punctuation character
- 51. Names cannot start with the letters xml (or XML, or Xml, etc)
- 52. Names cannot contain spaces
- 53. Any name can be used, no words are reserved.XML Markup DelimitersEvery XML element is made up of the following parts: Symbol Description < Start tag open delimiter </ End tag open delimiter something element name > tag close delimiter /> empty tag close delimiter
- 54. Different Types of XML Markups5 Types of Markup in XMLElementsEntitiesCommentsProcessing InstructionsIgnored Sections
- 55. Element MarkupElement MarkupIt is composed of 3 parts: start tag, the content, and the end tag.Example: <name>Neetu</name>The start tag and the end tag can be treated as wrappersThe element name that appears in the start tag must be exactly the same as the name that appears in the end tag.Example: <Name>Neetu</name>
- 56. Different Types of XML MarkupsAttribute MarkupAttributes are used to attach information to the information contained in an element.General syntax for attributes is:<elementname property = ‘value’> Or<elementname property = “value”>Attribute value must be enclosed within quotation marksUse either single quotes or double quotes but don’t mix them.
- 57. Attribute MarkupIf we specify the attributes for the same element more than once, the specifications are merged.<?xml version = “1.0”?><myparas><para num = “first”>This is Para 1 </para><para num = ‘second’ color = “red”>This is Para 2</para><myparas>
- 58. Attribute MarkupWhen the XML processor encounters line 3, it will record the fact that para element has the num attributeWhen it encounters the 4th line it will record the fact that para element has the color attribute
- 59. Reserved AttributeThe xml:lang attribute is reserved to identify the human language in which the element was writtenThe value of attribute is one of the following:en Englishfr Frenchde German
- 60. XML AttributesAttribute provides additional information about the element
- 61. Similar to attributes in HTML e.g., <IMG SRC=“sky.jpg”> In this SRC is the attribute
- 62. XML Attribute values must be quoted
- 63. XML elements can have attributes in name/value pairs just like in HTML.
- 64. In XML the attribute value must always be quoted.<note date = 01/01/2010> <---------- This is invalid<to>Priya</to><from>Deeali</from></note><note date = “01/01/2010”> --------- Now OK since enclosed in double quotes<note date = ‘01/01/2010’> --------- This is also OK since enclosed in single quotes
- 65. XML Attributes and ElementsConsider the following example:<person gender = "female"> <firstname>Geeta</firstname> <lastname>Shah</lastname></person>Gender is an attributeGender is an element<person> <gender>female</gender> <firstname>Geeta</firstname> <lastname>Shah</lastname></person>
- 66. Problems with XML AttributesAttributes cannot contain multiple values whereas elements can
- 67. Attributes cannot contain tree structures
- 68. Attributes are not easily expandable (for future changes)
- 69. Attributes are difficult to read and maintain
- 70. Use elements for data.
- 71. Use attributes for information that is not relevant to the data.Illustrating Problematic AttributesConsider the following example: <note day=“03" month="02" year="2010"to="Tina" from=“Yasmin" heading="Reminder"body=“Happy Birthday!"></note>Better way: <note> <date> <day>03</day> <month>02</month> <year>2010</year> </date> <to>Tina</to> <from>Yasmin</from> <heading>Reminder</heading> <body>Happy Birthday!</body></note>
- 72. When to use Attributes?XML Attributes can be used to assign ID references to elements.
- 73. Metadata – data about data – should be stored as attributes
- 74. The ID can then be used to identify the XML element <messages><note id="501"> <to>Tina</to> <from>Yasmin</from> <heading>Reminder</heading> <body>Happy Birthday!</body></note><note id="502"> <to>Yasmin</to> <from>Tina</from> <heading>Re: Reminder</heading> <body>Thank you, my dear</body></note></messages>
- 75. What does Extensible mean in XML?Consider the following XML example: <note> <to>Anita</to> <from>Veena</from> <body>You have an exam tomorrow</body></note> Suppose we create an application that extracted the <to>, <from> and <body> elements from the XML document to produce the result: MESSAGE To: AnitaFrom:Veena You have an exam tomorrow
- 76. What does Extensible mean in XML?Now suppose the author of the XML document added some extra information to it:<note><date>2008-01-10</date><to>Anita</to><from>Veena</from><heading>Reminder</heading><body>You have an exam tomorrow</body></note>
- 77. What does Extensible mean in XML?This application will not crash because it will still find the <to>, <from> and <body> elements in the XML document and produce the same output.
- 78. XML ValidationWhat is a “well formed” XML document?XML with correct syntax is "Well Formed" XML.A "Well Formed" XML document has correct XML syntax.XML documents must have a root elementXML elements must have a closing tagXML tags are case sensitiveXML elements must be properly nestedXML attribute values must be quoted
- 79. Wellformed Document - Rule 1Elements are case-sensitive.
- 80. If you define you language to use lowercase elements, then all instances of those elements must be in lowercase.Bad Examples…<H1>Sample Heading</H1><h1>Sample Heading</H1><H1>Sample Heading</h1>
- 81. Rule 2:All elements that contain text or other elements must have both start and ending tags.Rule 3:All empty elements (commonly known as standalone tags) must have a slash (/) before the end of the tag.Rule 4:All attribute values must be contained in quotes, either single or double – no exceptions!Rule 5:Elements may not overlap.
- 82. Elements must be nested properly within other elements and can not start before a sub-element and end within the sub-element. Rule 6:Isolated markup characters (characters essential to creating markup documents) may not appear in parsed content as is.
- 83. Isolated markup characters must be represented as a character entity and include the following: <, [, ], >, ', " and &.Isolated Markup Characters
- 84. These examples are invalid since they are both examples forgetting the semi-colon following the character entity.Bad Examples…<h1>Jack & Jill</h1><equation>5 < 2</equation>
- 85. Good Examples…<h1>Jack & Jill</h1><equation>5 < 2</equation>
- 86. Rule 7:Element (and attribute) names must start with either a letter (uppercase or lowercase) or a underscore.
- 87. Element names may contain letters, numbers, hyphens, periods and underscores inclusively.BAD EXAMPLES<bad*characters><illegal space><99number-start>GOOD EXAMPLES<example-one><_example2><Example.Three>
- 88. XML ValidationA “well formed” XML document conforms to the rules of a Document Type Definition (DTD) <?xml version="1.0" encoding="ISO-8859-1"?><!DOCTYPE note SYSTEM "Note.dtd"><note> <to>Tina</to> <from>Yasmin</from> <heading>Reminder</heading> <body>Happy Birthday!</body></note>
- 89. XML DTD – Document Type DefinitionThe DOCTYPE declaration in the example above, is a reference to an external DTD file. The content of the file is shown in the paragraph below.
- 90. The purpose of a DTD is to define the structure of an XML document. It defines the structure with a list of legal elements: <!DOCTYPE note[ <!ELEMENT note (to,from,heading,body)> <!ELEMENT to (#PCDATA)> <!ELEMENT from (#PCDATA)> <!ELEMENT heading (#PCDATA)> <!ELEMENT body (#PCDATA)>]>More on DOCTYPE laterViewing XML Files - 1
- 91. Viewing XML Files - 2The XML document will be displayed with color-coded root and child elements. A plus (+) or minus sign (-) to the left of the elements can be clicked to expand or collapse the element structure. To view the raw XML source (without the + and - signs), select "View Page Source" or "View Source" from the browser menu.
- 92. Viewing XML Files - 3Why XML documents display like this?XML documents do not carry information about how to display the data.Since XML tags are created by the user of the XML document, browsers do not know if a tag like <table> describes an HTML table or a dining table.Without any information about how to display the data, most browsers will just display the XML document as it is.
- 93. Using CSS to display XML FilesCSS (Cascading Style Sheets) can be used to format a XML document.Consider this XML document:
- 94. Displaying Formatted XML document-1<?xml version="1.0" encoding="ISO-8859-1"?><?xml-stylesheet type = "text/css" href = "birthdate.css"?><birthdate> <person> <name> <first>Anokhi</first> <last>Parikh</last> </name> <date> <month>01</month> <day>21</day> <year>1992</year> </date> </person></birthdate>
- 95. Displaying Formatted XML document-2Stylesheet – birthdate.cssbirthdate{ background-color: #ffffff; width: 100%;}person{ margin-left: 0;}name{ color: #FF0000; font-size: 20pt;}month, day, year{display:block; color: #000000; margin-left: 20pt;}
- 96. Final Output
- 97. XSLTXSL is a language for style sheets
- 98. An XSL style sheet is a file that describes how to display an XML document
- 99. XSL contains a transformation language for XML documents: XSLT. XSLT is used for generating HTML web pages from XML data.
- 100. XSLT - eXtensibleStylesheetLanguage Transformations
- 101. XSLT is used to transform an XML document into an HTML document
- 102. XSLT is the recommended style sheet language for XML