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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

XML – Extensible Markup Language

Sivakumar Kuttuva

& Janusz Zalewski

what is xml
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

how xml look like
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>

why xml came into existence 1
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.
why xml came into existence 2
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.
two types of syntax standards
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).

well formed xml
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 />
why well formed matters
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.
valid xml
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)>
valid xml1
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.
a sample entry in the xml file adhering to the given dtd
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>
why use dtd
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.
the components line 1
The Components – Line 1
  • <!ELEMENT Bookcatalog (Book+)>
  • Bookcatalog is the root element.
  • Bookcatalog can have one or more (indicated by the +) Book elements.
the components line 2
The Components – Line 2
  • <!ELEMENT Book (Title, Author, Publisher, Price)>
  • Each Book element can contain:
  • A title, author, publisher, price
the components line 4
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.
the components lines 5 9
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;.
schemas
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
dtds vs schemas
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
css and xml
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”?}
css and xsl
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
xsl extensible style language
XSL (Extensible Style Language)
  • XSL comes from DSSSL (Document Style Semantics and Specification Language), the SGML style language, derived from LISP.
benefits of xsl
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.

advanced features of xml
Advanced Features of XML
  • Xlink
  • Xpointer
  • Parsing XML with DOM

(Document Object Model)

  • XPath
xml applications
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.
future demands of xml
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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