Introduction to XML

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Discuss markup language
List and explain drawbacks of HTML
Discuss the architecture of XML documents
List the benefits of XML
Discuss Parser

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Introduction to XML

  1. 1. 1 Introduction to XML Chapter 1
  2. 2. Core XML / Chapter 1 / Slide 2 of 352 Chapter Objectives -1  Discuss markup language  List and explain drawbacks of HTML  Discuss the architecture of XML documents  List the benefits of XML  Discuss Parser
  3. 3. Core XML / Chapter 1 / Slide 3 of 353 Chapter Objectives -2  Build a complete XML Document:  Character Data  Comments  Processing Instructions  Entities  General Entities  Parameter Entities  The DOCTYPE Declarations
  4. 4. Core XML / Chapter 1 / Slide 4 of 354 History of Markup Documents recorded using paper and pen Typesetters formatting documents Tools used by typesetters to format a document
  5. 5. Core XML / Chapter 1 / Slide 5 of 355 Markup Language  A Markup language defines the rules that help to add meaning to the content and structure of documents.  They are classified as:  Stylistic Markup – It determines the presentation of the document  Structure Markup – It defines the structure of the document  Semantic Markup – It determines the content of the document
  6. 6. Core XML / Chapter 1 / Slide 6 of 356 SGML  Generalized Markup Language (GML) is the system of formatting documents.  GML was fine-tuned and came to be known as Standard Generalized Markup Language (SGML).  SGML is the source of origin of all markup languages
  7. 7. Core XML / Chapter 1 / Slide 7 of 357 Features of SGML  It describes markup language, which allows authors to create their own tags that relate to their content.  It needs a separate file that will contain all the rules for the language, for its interpretation  A SGML application is markup language derived from SGML.
  8. 8. Core XML / Chapter 1 / Slide 8 of 358 HTML  HTML is the most famous markup language derived from SGML.  It was created to mark up technical papers so that they could be transferred across different platforms for the scientific community.  It is now also used by those non-scientific users who are concerned about their document’s presentation.
  9. 9. Core XML / Chapter 1 / Slide 9 of 359 Drawbacks of HTML  Fixed tag set  Presentation technology does not relate to the contents  It is flat  Clogging  HTML is not international  Data interchange is impossible  Does not have a robust linking mechanism  HTML is not reusable
  10. 10. Core XML / Chapter 1 / Slide 10 of 3510 HTML and XML code Examples <UL> <LI> TOM CRUISE <UL> <LI> CLIENT ID : 100 <LI> COMPANY : XYZ Corp. <LI> Email : tom@usa.net <LI> Phone : 3336767 <LI> Street Adress: 25th St. <LI> City : Toronto <LI> State : Toronto <LI> Zip : 20056 </UL> </UL> <Details> <CONTACT> <PERSON_NAME>TOM CRUISE </PERSON_NAME> <ID> 100 </ID> <Company>XYZ Corp. </Company> <Email> tom@usa.net</Email> <Phone> 3336767 </Phone> <Street> 25th St. </Street> <City> Toronto </City> <State> Toronto </State> <ZIP> 20056 </ZIP> </CONTACT> </Details> HTML Code XML Code
  11. 11. Core XML / Chapter 1 / Slide 11 of 3511 XML -1  XML stands for Extensible Markup Language.  It overcomes all the drawbacks of HTML.  It allows the user to define their own set of tags, and also makes it possible for others (people or programs) to understand it.  It is more flexible than HTML.  It inherits the features of SGML and combines it with the features of HTML.  It is a smaller version of SGML.
  12. 12. Core XML / Chapter 1 / Slide 12 of 3512 XML -2  XML is a metalanguage and it describes other languages.  The data contained in an XML file can be displayed in different ways.  It can also be offered to other applications for further processing.  Style sheets help transform structured data into different HTML views. This enables data to be displayed on different browsers.
  13. 13. Core XML / Chapter 1 / Slide 13 of 3513 XML Architecture - 1  XML supports three-tier architecture for handling and manipulating data.  It can be generated from existing databases using a scalable three-tier model.  XML tags represent the logical structure of data that can be interpreted and used in various ways by different applications.  The middle-tier is used to access multiple databases and translate data into XML.
  14. 14. Core XML / Chapter 1 / Slide 14 of 3514 XML Architecture -2
  15. 15. Core XML / Chapter 1 / Slide 15 of 3515 XML – A Universal data format  HTML is a single markup language, but XML is a family of markup languages.  Any type of data can be easily defined in XML.  XML is popular because it supports a wide range of applications and is easy to use.  XML has a structured data format, which allows it to store complex data
  16. 16. Core XML / Chapter 1 / Slide 16 of 3516 Benefits of XML  The three-tier architecture has easier scalability and better security.  The benefits of XML are classified into the following:  Business benefits  Technological benefits
  17. 17. Core XML / Chapter 1 / Slide 17 of 3517 Business Benefits  Information sharing:  Allows businesses to define data formats in XML  Provides tools to read, write and transform data between XML and other formats  XML inside a single application:  Powerful, flexible and extensible language  Content Delivery:  Supports different users and channels, like digital TV, phone, web and multimedia kiosks
  18. 18. Core XML / Chapter 1 / Slide 18 of 3518 Technological Benefits Technological Benefits Re-use of data Separation of data and presentation ExtensibilitySemantic information
  19. 19. Core XML / Chapter 1 / Slide 19 of 3519 XML Document Structure  An XML document is composed of sets of “entities” identified by unique names.  All documents begin with a root or document entity.  Entities are aliases for more complex functions.  Documents are logically composed of declarations, elements, comments, character references, and processing instructions.
  20. 20. Core XML / Chapter 1 / Slide 20 of 3520 Well formed and Valid Documents  An XML document is considered as well formed, if a minimum set of requirements defined in the XML 1.0 specification are satisfied.  The requirements ensure that correct language terms are used in the right manner .  A valid XML document is a well-formed XML document, which conforms to the rules of a Document Type Definition (DTD).  DTD defines the rules that an XML markup in the XML document must follow.
  21. 21. Core XML / Chapter 1 / Slide 21 of 3521 Parsers - 1  Parsers help the computer interpret an XML file. <?xml version=“1.0”? > <nxn> </nxn> Editor with the XML document Parsed document viewed in the browser XML document parsed by the parser Their are two types of parsers: Non Validating parser Validating parser
  22. 22. Core XML / Chapter 1 / Slide 22 of 3522 Parsers - 2 XML file Other related files (like DTD file) Parsers load the XML and other related files to check whether the XML document is well formed and valid Data tree
  23. 23. Core XML / Chapter 1 / Slide 23 of 3523 Data versus Markup <NAME> Tom Cruise </NAME> Markup Data
  24. 24. Core XML / Chapter 1 / Slide 24 of 3524 Creating an XML Document  To create an XML document:  State an XML declaration  Create a root element  Create the XML code  Verify the document
  25. 25. Core XML / Chapter 1 / Slide 25 of 3525 Stating an XML Declaration  Syntax <?xml version=“1.0” standalone=“no” encoding=“UTP-8”?>  ‘Standalone’ and ‘encoding’ attributes are optional, only the version number is mandatory  ‘Standalone’ – is the external declaration  ‘Encoding’ - specifies the character encoding used by the author  XML 1.0 version is default
  26. 26. Core XML / Chapter 1 / Slide 26 of 3526 Creating a Root Element  There can only be one root element  It describes the function of the document  Every XML document must have a root element Example <?xml version=“1.0” standalone=“no” encoding=“UTP-8”?> <BOOK> </BOOK>
  27. 27. Core XML / Chapter 1 / Slide 27 of 3527 Creating the XML Code -1  It is the process of creating our own elements and attributes as required by our application.  Elements are the basic units of XML content.  Tags tell the user agent to do something to the content encased between the start and end tag.Opening Tag Content Closing Tag <TITLE> Aptech Ltd </TITLE> Element Parts of an element
  28. 28. Core XML / Chapter 1 / Slide 28 of 3528 Creating the XML Code -2  Rules govern the elements:  At least one element required  XML tags are case sensitive  End the tags correctly  Nest tags Properly  Use legal tags  Length of markup names  Define Valid Attributes
  29. 29. Core XML / Chapter 1 / Slide 29 of 3529 Verify the document  The document should follow the XML rules; otherwise it will not be read by the browser or by any other XML reader
  30. 30. Core XML / Chapter 1 / Slide 30 of 3530 Comments  This is information for the understanding of the user, and is to be ignored by the processor.  Syntax <!- - Write the comment here -- > Example <!-- don't show these <NAME>KATE WINSLET</NAME> <NAME>NICOLE KIDMAN</NAME> <NAME>ARNOLD</NAME> --> <NAME>TOM CRUISE</NAME> The example given will display only the name TOM CRUSIE, and others are treated as comments.
  31. 31. Core XML / Chapter 1 / Slide 31 of 3531 Processing Instruction  A processing information is a bit of information meant for the application using the XML document.  These instructions are directly passed to the application using the parser.  The XML declaration is also a processing agent. <?xml:stylesheet type=“text/xsl”?> Name of application Instruction information
  32. 32. Core XML / Chapter 1 / Slide 32 of 3532 Character Data  The text between the start and end tags is defined as ‘character data’.  Character data may be any legal (Unicode).  Character data is classified into:  PCDATA  CDATA
  33. 33. Core XML / Chapter 1 / Slide 33 of 3533 PCDATA  It stands for parsed character data.  PCDATA is text that will be parsed by a Parser.  Tags inside the text will be treated as markup and entities will be expanded. Entity Name Character &lt; < &gt; > &amp; & &quot; " &apos; ' Predefined entities
  34. 34. Core XML / Chapter 1 / Slide 34 of 3534 CDATA  It means character data.  It will not be parsed by the Parser.  CDATA are used to make it convenient to include large blocks of special characters.  The character string ]]> is not allowed within a CDATA block as it will signal the end of the CDATA block. <SAMPLE> <![CDATA[<DOCUMENT> <NAME>TOM CRUISE</NAME> <EMAIL>tom@usa.com</EMAIL> </DOCUMENT>]]> </SAMPLE> Example
  35. 35. Core XML / Chapter 1 / Slide 35 of 3535 Entities  Entities are used to avoid typing long pieces of text repeatedly within a document.  There are two categories of entities:  General entities Syntax <!ENTITY ADDRESS "text that is to be represented by an entity">  Parameter entities Syntax <!ENTITY % ADDRESS "text that is to be represented by an entity">
  36. 36. Core XML / Chapter 1 / Slide 36 of 3536 Examples of Entities An example of Parameter entities < CLIENT = "&APTECH;" PRODUCT = "&PRODUCT_ID;" QUANTITY = "15">  Entity declaration  Syntax %PARAMETER_ENTITY_NAME ;  Example %address; An example of a General entity <!ENTITY full_address " My Address 12 Tenth Ave. Suite 12 Paris, France">  Entity declaration  Syntax &ENTITY_NAME;  Example &address;
  37. 37. Core XML / Chapter 1 / Slide 37 of 3537 The DOCTYPE declarations  The <!DOCTYPE [..]> declaration follows the XML declaration in an XML document.  Syntax <?xml version="1.0"?> <!DOCTYPE myDoc [ ...declare the entities here.... <myDoc> ...body of the document.... </myDoc> Example <!DOCTYPE CUSTOMERS [ <!ENTITY firstFloor "15 Downing St Floor 1"> <!ENTITY secondFloor "15 Downing St Floor 2"> <!ENTITY thirdFloor "15 Downing St Floor 3"> ]>
  38. 38. Core XML / Chapter 1 / Slide 38 of 3538 Attributes  An attribute gives information about an element.  Attributes are embedded in the element start tag.  An attribute consists of an attribute name and attribute value. Example <TV count="8">SONY</TV> <LAPTOP count="10">IBM</LAPTOP>
  39. 39. Core XML / Chapter 1 / Slide 39 of 3539 Summary-1  A markup language defines a set of rules that adds meaning to the content and structure of documents  XML is extensible, which means that we can define our own set of tags, and make it possible for other parties (people or programs) to know and understand these tags. This makes XML much more flexible than HTML  XML inherits features from SGML and includes the features of HTML. XML can be generated from existing databases using a scalable three-tier model. XML-based data does not contain information about how data should be displayed  An XML document is composed of a set of “entities” identified by unique names
  40. 40. Core XML / Chapter 1 / Slide 40 of 3540 Summary-2  A well-formed document is one that conforms to the basic rules of XML; a valid document is a well-formed document that conforms to the rules of a DTD (Document Type Definition)  The parser helps the computer to interpret an XML file  Steps involved in the building of an XML document are:  Stating an XML declaration  Creating a root element  Creating the XML code  Verifying the document  Character data is classified into PCDATA and CDATA
  41. 41. Core XML / Chapter 1 / Slide 41 of 3541 Summary-3  Entities are used to avoid typing long pieces of text repeatedly in a document. The two types of entities are:  General entities  Parameter entities  The <!DOCTYPE […]> declaration follows the XML declaration in an XML document.  An attribute gives information about an element

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