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XML – Extensible Markup Language

XML – Extensible Markup Language. Sivakumar Kuttuva & Janus z Zalewski. What is XML?. Extensible Markup Language (XML) is a universal standard for electronic data exchange

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XML – Extensible Markup Language

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  1. XML – Extensible Markup Language Sivakumar Kuttuva & Janusz Zalewski

  2. What is XML? Extensible Markup Language (XML) is a universal standard for electronic data exchange Provides a method of creating and using tags to identify the structure and contents of a document ignoring the formatting

  3. How XML look like <?xml version="1.0"?><Course> //Root Tag <Name>Java Programming</Name> //Element Course Name  <Department>EECS</Department> //Element Dept   <Teacher>    <Name>Paul</Name>  </Teacher>  <Student>    <Name>Ron</Name>  </Student>  <Student>    <Name>Uma</Name>  </Student>  <Student>    <Name>Lindsay</Name>  </Student></Course>

  4. Why XML came into existence?(1) • Make it easier to provide metadata -- data about information   <Department>EECS</Department>  <Teacher>    <Name>Paul Thompson</Name>  </Teacher>Here Name,Department are Metadata • Large-scale electronic publishing requires dynamic documents without changing document formats. • Internationalized media-independent electronic publishing.

  5. Why XML came into existence? (2) • Allow industries to define platform-independent protocols for the exchange of data, especially the data of electronic commerce. • Make it easy for people to process data using inexpensive software.

  6. Two Types of Syntax Standards • XML documents must meet one of two syntax standards: • Well-formed (the basic standard) Document must meet minimum, standard criteria. • Valid Document must be well-formed and adhere to a DTD (Document Type Definition).

  7. Well-Formed XML • Well-formed criteria include: • All elements have a start and end tag with matching capitalization. • <B></B> • Proper element nesting. • <B><I></I></B> • not <B><I></B></I> • Attribute values are in single or double quotes. • <book call_no=" 3456-34567890-3456 "> • Empty elements need an end or closed start tag. • <IMG></IMG> or <IMG />

  8. Why Well-Formed Matters • Guarantees the document’s syntax before sending it to an application. • A clean syntax guarantee which means less ambiguity which results in faster processing. • A well-formed violation is a fatal error.

  9. Valid XML • To be valid, a document must be well-formed and adhere to a DTD. • A DTD Example is shown below • <!ELEMENT BOOKCATALOG (BOOK)+> • <!ELEMENT BOOK (TITLE, AUTHOR+, PUBLISHER?,PRICE?> • <!ATTLIST BOOK ISBN CDATA #REQUIRED> • <!ATTLIST BOOK BOOKTYPE (Fiction|SciFi|Fantasy) #IMPLIED> • <!ELEMENT TITLE (#PCDATA)> • <!ELEMENT AUTHOR (LASTNAME)> • <!ELEMENT LASTNAME (#PCDATA)> • <!ELEMENT PUBLISHER (#PCDATA)> • <!ELEMENT PRICE (#PCDATA)>

  10. Valid XML • DTD - Document Type Definition specifies: • Elements in the document. • Author, Publisher • Their attributes. • For Book Author, Publisher, Price are attributes • Whether they are mandatory or optional • A DTD effectively specifies the document’s grammatical rules.

  11. A sample entry in the XML file adhering to the given DTD • <BOOKCATALOG> • <BOOK> • <ISBN>3456-34567890-3456</ISBN> • <TITLE>C++ Primer</TITLE> • <AUTHOR_LASTNAME>Tendulkar</AUTHOR_LASTNAME> • <PUBLISHER>McGraw Hill</PUBLISHER> • <PRICE>41.99</PRICE></BOOK> • </BOOKCATALOG>

  12. Why use DTD • Well-formed means the document meets a minimum standard set of rules. • A DTD helps to define user defined rules and languages provided the XML content adheres to the syntax standards likeWML, MAML, etc.

  13. The Components – Line 1 • <!ELEMENT Bookcatalog (Book+)> • Bookcatalog is the root element. • Bookcatalog can have one or more (indicated by the +) Book elements.

  14. The Components – Line 2 • <!ELEMENT Book (Title, Author, Publisher, Price)> • Each Book element can contain: • A title, author, publisher, price

  15. The Components – Line 4 • <!ATTLIST Book BookType (Fiction | SciFi | Nonfiction) Fiction. • Each Book element has a attribute BookType Three options (indicated by |) Fiction, SciFi and Non-Fiction with Fiction as default.

  16. The Components – Lines 5-9 • The Remaining Elements Title through Price are #PCDATA • Parseable character data that the processor will check for entities and markup characters • Any <,>, or & in data specified as PCDATA must be represented by &lt; or &gt; or &amp;.

  17. Schemas • The next step beyond DTDs • Come from the database world • More powerful and extensible than DTDs, which come from the SGML world • Schemas are XML documents, so they: • Are extensible • Use XML syntax unlike DTDs • Support data types like dates, times, currencies, important in eCommerce

  18. DTDs vs Schemas • Why use schemas? • More powerful than DTDs • Better suited for eCommerce. • Why use DTDs? • Wider tool support. • More examples available for use and reference. • HTML,XHTML,CALS,etc. • Greater depth of experience in the industry • Wider pool of developers

  19. CSS and XML • CSS was designed for HTML but works fine under XML as well. • Rather than create an XSL style sheet, you can create a simpler CSS and attach it to a XML document via a command like: • {?xml-stylesheet href=“mycss.css” type=“text/css”?}

  20. CSS and XSL • XML uses custom tags that a browser does not know how to display • So XML documents may display like this • <BOOKCATALOG> • <BOOK> • <ISBN>3456-34567890-3456</ISBN> • <TITLE>C++ Primer</TITLE> • <AUTHOR_LASTNAME>Tendulkar</AUTHOR_LASTNAME> • <PUBLISHER>McGraw Hill</PUBLISHER> • <PRICE>41.99</PRICE></BOOK> • </BOOKCATALOG> • Legibility requires applying styles: • – CSS • – XSL

  21. XSL (Extensible Style Language) • XSL comes from DSSSL (Document Style Semantics and Specification Language), the SGML style language, derived from LISP.

  22. Benefits of XSL • An XSL style sheet is well-formed XML. • Supports a style sheet DTD for validation. • Far greater processing ability than CSS. • XSL Transformations (XSLT) take part ofan XML document and transform it, such as XML to HTML. – This is why XML appears to be the route to single-sourcing.

  23. Advanced Features of XML • Xlink • Xpointer • Parsing XML with DOM (Document Object Model) • XPath

  24. XML Applications • Applications that require the Web client to mediate between two or more heterogeneous databases like information tracking system for a home health care agency. • Applications that attempt to distribute a significant proportion of the processing load from the Web server to the Web client like technicaldata delivery system for a wide range of products. • Applications that require the Web client to present different views of the same data to different users. • Applications in which intelligent Web agents attempt to tailor information discovery to the needs of individual users.

  25. Future Demands of XML • Intelligent Web agents would have demand for structured data • User preferences must be represented in a standard way to mass media providers.

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