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Comp2513 XML – eXtensible Markup Language

Comp2513 XML – eXtensible Markup Language. Daniel L. Silver, Ph.D. Objectives. To discuss problems with the HTML based web and introduce XML (and related methods) as the next generation markup language References: DDEA Ch. 8, Sharma Ch.7 and External Web Links. Outline.

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Comp2513 XML – eXtensible Markup Language

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  1. Comp2513XML – eXtensible Markup Language Daniel L. Silver, Ph.D.

  2. Objectives • To discuss problems with the HTML based web and introduce XML (and related methods) as the next generation markup language • References: DDEA Ch. 8, Sharma Ch.7 and External Web Links Daniel L. Silver

  3. Outline • Problems with the HTML based Web • The XML idea • XML fundamentals • XML use Daniel L. Silver

  4. Problems with the HTML based Web • HTML documents focus on display and not structure and meaning of data - an information maze devoid of meaning • Inefficient use of tags (every instance of data must be tagged) • Fixed number of tags - can not be extended (not extensible) • HTML search is based on keywords without context • Client-server applications cannot easily exchange data using HTML Daniel L. Silver

  5. HTML focuses on display syntax • HTML tags such as <B>Simpson<\B> tell how to display the word “Simpson” • Focus is on presentation (format, syntax) • But its does not define what “Simpson” means • A persons name? A city? A company? • Or its structural relationship to other data • Full name? Last name? First name? Daniel L. Silver

  6. The XML idea • eXtensible Markup Language • XML defines meaning (semantics): <lname>Simpson<\lname> • In terms of structural relationships … • Independent of presentation <mail_adrs> <fname>Homer<\fname> <lname>Simpson<\lname> <strnum>1234<\strnum> <str>Hickup Lane<\str> <\mail_adrs> Daniel L. Silver

  7. What is XML? • 1996 - A simplified form of SGML for the web (Standardized General Markup Language) • Both machine and human readable • Separates content, structure and presentation • Extensible (users can define structure and meaning) • Supports information reuse and processing autonomy (application decides how to use/present) SGML XML HTML Daniel L. Silver

  8. The W3C’s Basic Requirements for XML • XML shall be straightforwardly usable over the Internet. • XML shall support a wide variety of applications. • XML shall be compatible with SGML. • It shall be easy to write programs which process XML documents. • The number of optional features in XML is to be kept to the absolute minimum, ideally zero. • XML documents should be human-legible and reasonably clear. • XML documents should be easy to prepare. • The design of XML shall be formal and concise. • Terseness in XML markup is of minimal importance. Daniel L. Silver

  9. XML Fundamentals <?xml version = "1.0"?> … <contacts> <contact> <LastName>Black</LastName> <FirstName>John</FirstName> </contact> … </contacts> <!ELEMENT contacts (contact)* > <!ELEMENT contact (LastName, FirstName) > <!ELEMENT LastName (#PCDATA) > <!ELEMENT FirstName (#PCDATA) > DTD Structure Presentation in Context XML Content XSL Presentation <?xml version="1.0"?> <xsl:stylesheet xmlns:xsl = "http://www.w3.org/TR/WD-xsl"> … Daniel L. Silver

  10. XML’s Intended Use • Standard format for exchanging data • Promote cross-platform and cross-application schema – independent of data content, use and presentation • Oriented toward giving meaning to data, and does not emphasize display issues • Client – describes valid data for display • Server – describes valid data for exchange Daniel L. Silver

  11. XMLs Intended Use • Allows organizations to maintain proprietary databases while at the same time communicate information with one another • Schemas for specific domains have been created: • Music • Chemical symbols • Mathematical formulas • Common industry models (EDI for B2B) • Web resource descriptions (directories, addresses) Daniel L. Silver

  12. XML versus HTML • XML is not a replacement for HTML • XML and HTML were designed with different goals: • HTML was designed to display data and to focus on how data looks • XML was designed to describe data and to focus on what data means • They complement each other Daniel L. Silver

  13. XML eXtensibility • XML allows you to create your own definitions of data and there relationship to other pieces of data • Thus the name eXtensible • ** Note that XML is case sensitive ** <?xml version="1.0"?> <People> <Person> <Name> <First>Patrick</First> <Last>Joe</Last> </Name> </Person> </People> Daniel L. Silver

  14. Using IE to Explore XML • You can use Internet Explorer to view an XML document directly • A plus (+) or minus sign (-) to the left of the XML elements can be clicked to expand or collapse the element structure • Or view the raw XML source using "View Source" from the browser menu • Example: cd_catalog.xml Daniel L. Silver

  15. Defining XML Structure • DTD – Document Type Definition defines the fields in an XML document and their relation to one another (schema) • Meta-data : data about data • Can be included in .xml file or referenced as a .dtd file • Used by applications to validate XML data <!ELMENT People (Person)* > <!ELMENT Person (Name) > <!ELMENT Name (First, Last) > <!ELMENT First (#PCDATA) > <!ELMENT Last (#PCDATA) > Daniel L. Silver

  16. Processing an XML Document <?xml version="1.0"?> <People> <Person> <Name> <First>Patrick</First> <Last>Joe</Last> </Name> </Person> </People> <!ELMENT People (Person)* > <!ELMENT Person (Name) > <!ELMENT Name (First, Last) > <!ELMENT First (#PCDATA) > <!ELMENT Last (#PCDATA) > DTD Structure XML Content • An application that wishes to use XML • data should parse the data using a DTD. • There are two approaches: • DOM – read the entire document using the • DTD and build a tree of elements • SAX – parse on demand (interactively) • as each new element is encountered DOM = Document Object Model SAX = Simple API for XML Daniel L. Silver

  17. Processing an XML Document • Internet Explorer 5.0 (+) has a built in DOM-based XML parser, msxml • DTD can be embedded in XML or referenced • Examples: • simple_example.xml with DTD embedded • letter.xml and letter.dtd Daniel L. Silver

  18. Displaying XML Documents • Can be accomplished in various ways, any program that can parse the XML can display the information • Here is a simple HTML solution … • simple_contact.html - XML is embedded, DTD is not required • Javascript could be used instead • article.xml and DOMexample.html • note.xml and note.html Daniel L. Silver

  19. Displaying XML Documents • An XSL – eXtensible Stylesheet Layout can be used • Examples: Basic - contact3.xml using contact_list3.xsl Full function – contact.xml using contact_list.xsl Handheld – contact2.xml using contact_list2.xsl <?xml version="1.0"?> <xsl:stylesheet xmlns:xsl = "http://www.w3.org/TR/WD-xsl"> … Daniel L. Silver

  20. Transferring Data with XML • It is possible to use XML as a method of transferring meaningful data between applications even when application databases do not match • Adherence to XML DTD is the key ODBC JDBC XML DB2 App A App B Oracle Common DTD Daniel L. Silver

  21. Smart Searches on the Internet • With XML and DTDs, keyword searches on the Internet can now be aimed at the appropriate systems, databases, pages • A syntactic search using IE: “cook New York kitchen restaurant” … would become … • A semantic search: <occupation>cook</occupation> <city>New York</city> Daniel L. Silver

  22. VXML • Voice XML • Sound embedded as content and processed as per style sheet • Other media types will be used as well Daniel L. Silver

  23. eadmin and XML • Eadmin • load.jsp?id=91 • servlet/LoadStore • StoreLoader(store,xmlfile) store.xml store.dtd Daniel L. Silver

  24. References • http://www.w3.org/XML/ • http://www.xmlfiles.com/xml/ Daniel L. Silver

  25. THE ENDdanny.silver@acadiau.ca

  26. XML • eXtensible Markup Language • HTML tags such as <B>Silver<\B> tell how to display the word “Silver” • But its does not define what it means • XML defines meaning: <last_name>Silver<\last_name> • And to create structure … Daniel L. Silver

  27. Major Architectural Components of the Web Bank Server Client 1 Dedicated Browser HTTP TCP/IP Server A HTTP Server App. Server Database Server Internet Client 2 Browser prog.cgi URL index.html Server B Bank Server Daniel L. Silver

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