Extensible Markup Language

1
Extensible Markup Language

• Presented by
• Billy Jimenez
• Mike Evans
• Matt Lietzke
• Doug Svendsen

2
The Basics

• What is XML?
• XML is a markup language which used to define
  data. It can be used across many platforms to
  transmit information
• What does XML Do?
• Nothing

3
Uses of XML

• Separate data from HTML
• Share and exchange data
• Store data
• Make data more useful

4
XML Syntax

• XML declaration
• Describe child elements
• Define the end of the root element
• lt?xml version"1.0" encoding"ISO-8859-1"?gt
• ltnotegt
• lttogtClasslt/togt
• ltfromgtTeam twolt/fromgt
• ltheadinggtXMLlt/headinggt
• ltbodygtThis is what XML looks likelt/bodygt
• lt/notegt

5
XML Tags

• All elements of XML must have closing tags
• ltnotokgtDont do this
• ltokgtHooray for closing tablt/okgt
• XML tags are case sensitive
• ltUpperCasegtNot going to worklt/UPPERCASEgt
• ltUpperCasegtGoing to worklt/UpperCasegt
• Must properly nest elements
• ltingtltordergtnot properly nestedlt/ingtlt/ordergt
• ltingtltordergtproperly nestedlt/ordergtlt/ingt

6
More on XML Tags

• Root element is necessary for XML documents
• ltrootgt
• ltchildgt.lt/childgt
• lt/rootgt
• Always quote attribute values
• lt?xml version1.0 encodingISO-4234-m
• White space is preserved in XML
• Commenting in XML
• lt! This is how you comment --gt

7
XML Elements

• XML documents may carry more information than
  what is read and output
• XML elements have parent/child relationships
• Element naming rules
• May not begin with punctuation or a number
• May not begin with xml or any case combination
• May not contain spaces
• Ex. ltcustom_name5gt

8
XML Attributes

• Attributes may be used to add information about
  elements
• Attributes written with single or double quotes
• ltteam team2awesomegt
• ltteam team2awesomegt
• If the attribute contains quotes, must use the
  opposite type to include them
• ltteam team2we are awesomegt
• ltteam team2we are awesomegt

9
Attributes vs Children

• Attributes may also be written as child elements
• ltnote date12/08/2005gt
• ltdategt
• ltmonthgt12lt/monthgt
• ltdaygt08lt/daygt
• ltyeargt2005lt/yeargt
• lt/dategt
• Disadvantages to attributes
• Cannot contain multiple values
• Cannot describe structures
• More difficult for program code to read

10
Sax Parser and Echoing

• Create a skeleton for the app
• public class Echo
• public static void main(String argv)
• Import classes app will use
• Set up I/O
• Implement ContentHandler Interface

11
Setting up the Parser

• Public static void main(String argv)
• if(argv.length !1)
• System.err.println("Usage cmd filename")
• System.exit(1)
• DefaultHandler handler new Echo()
• // Use non-validating parser
• SAXParserFactory factory SAXParserFactory.newIn
  stance()
• try
• // Set up the output stream
• out new OutputStreamWriter(System.out,
  UTF8)
• // Parse the input
• SAXParser saxParser factory.newSASParser()
• saxParser.parse( new File(argv0), handler )
• catch(Throwable t)
• t.printSatckTrace)
• stystem.exit(0)

12
Write the Output

• static private Writer out
• private void emit(String s) throws SAXException
  
• try
• out.write(s)
• out.flush()
• catch (IOException e)
• throw new SAXException("I/O error", e)

13
Space the Output

• private void nl() throws SAXException
• String lineEnd System.getProperty("line.separat
  or")
• try
• out.write(lineEnd)
• catch (IOException e)
• throw new SAXException("I/O error", e)

14
Identify Events

• To identify events, one must overwrite 5
  important function
• Start Document()
• Start element(String namespaceURI,
  String sName, // simple name
  (localName) String
  qName, // qualified name,Attributes attrs)
• End element (String namespaceURI,
  String sName, // simple name
  String qName // qualified name)
• Characters(char buf, int offset, int len)
• End Document()

15
SAX Usages

• What is SAX Used for?

16
Document Type Definition (DTD)

• DTD defines the structure of a XML document
• Lets you specify the kinds of tags and elements
  that can be included in XML documents
• DTD is a description of an XML files format,
  allowing outside sources to parse it

17
Basic Implementation of DTD

• DTD tags
• Syntax
• lt!ELEMENT element-name categorygt
• Or lt!ELEMENT element-name (element-content)gt
• (element-content) allows for nested elements
• Example
• lt!ELEMENT note (message)gt
• lt!ELEMENT message (PCDATA)gt

18
Defining Nested Elements and Text

• lt!ELEMENT media(song, book, article, movie)gt
• lt!ELEMENT book(title, author, summary,
  publisher)gt
• lt!ELEMENT title(PCDATA)gt
• PCDATA parsed character data or text
• denotes a special word rather than an element

19
Limitations of DTD

• Syntax is different from XML
• No way define what format PCDATA is
• i.e. only numbers or date
• DTD can ONLY specify a documents structure, it
  cannot limit content

20
DOM

• What is DOM?
• - DOM is an organization of some described data
  that allows the user to access and change the
  data.
• 1. HTML DOM
• 2. XML DOM
• XML DOM
• Platform and language independent
• Defines a standard set of objects for XML
• Is a W3C standard

21
Reading XML into DOM

• Declaring DOM
• variableType xmlDoc new ActiveXObject("Microsof
  t.XMLDOM")
• Error handling
• - outputs an error file in XML
• Load the Specified File
• xmlDoc.load(file_name.xml")

22
Reading XML into DOM

• Parse the file
• for each x in xmlDoc.documentElement.childNodes
  document.write(x.nodename)
• document.write(" ")
• document.write(x.text)
• next
• Manipulate Data
• nodes xmlDoc.documentElement.childNodes

23
JTree construction from DOM

• Compress the tree view
• Make operation selectable
• Identify nodes

24
Application of XML

• GML
• OpenOffice
• Chemistry
• Pharmaceuticals
• Webpage building
• Contracts
• Court filings
• Insurance

25
Sources

• Ray, Erik T. Learning XML. 2nd ed. Beijing
  Cambridge, Mass. O'Reilly, 2003.
• Lu, Shiyong, et al. "On the Consistency of XML
  DTDs." Data Knowledge Engineering 52.2 (2005)
  231-47.
• Armstrong, Eric. "Working with XML
• The Java API for Xml Processing (JAXP) Tutorial."
  Sun MicroSystems. December 10, 2001. Sun
  Microsystems. 12/05/05 lthttp//java.sun.com/webser
  vices/jaxp/dist/1.1/docs/tutorial/sax/index.htmlgt.
  
• "XML DOM Introduction" 2005. W3Schools. 3 Dec.
  2005 lthttp//www.w3schools.com/dom/dom_intro.aspgt.
  
• Lake, Ron. "The Application of Geography Markup
  Language (GML) to the Geological Sciences."
  Computers Geosciences 31.9 (2005) 1081-94.
  lthttp//www.sciencedirect.com/science/article/B6V7
  D-4GSJR67-1/2/67d38d2783fcf67313caf1d794a95253gt.