XML An Introduction

1
XML An Introduction

• Structured Data Mark-up
• James McCartney
• CSCE 590, Cluster and Grid Computing

2
Why XML?

• Allows creation of standardized markup.
• Separates presentation logic from data.
• Allows for multiple dynamic client applications.
• Mandates machine readable, rational tags for
  describing data.
• Support for wide ranging industry needs.

3
XML Requirements

• Identify all types of information making up the
  content of your document.
• Define the structure of each distinct type of
  information you are including in your document.

4
Tags, elements, and attributes.

• ltaddressgt
• ltnamegt
• lttitlegtMrs.lt/titlegt
• ltfirst-namegt
• Mary
• lt/first-namegt
• ltlast-namegt
• McGoon
• lt/last-namegt
• lt/namegt
• ltstreetgt
• 1401 Main Street
• lt/streetgt
• ltcity state"NC"gtAnytownlt/citygt
• ltpostal-codegt
• 34829
• lt/postal-codegt
• lt/addressgt

• A tag is a value between the less than (lt) and
  greater than (gt) angle brackets.
• An element includes the starting and ending tag,
  and everything between the two. This includes
  other (child) elements.
• An attribute is a name value pair that is located
  in the opening tag of an element

5
Document States

• Valid Documents abide by the XML syntax for
  document markup and follow the rules defined by
  their DTD and Schema definition.
• Invalid Documents have syntax errors that dont
  conform to XML rules.
• Well-formed Documents follow XML syntax rules,
  but dont have a DTD or Schema definition.

6
XML Structure

• General Structure of an XML Document

7
XML Rules

• An XML document must contain a single root
  element.
• Elements cant overlap (jump levels).
• End tags are required (at least lttag /gt).
• Element names are case sensitive.
• Attributes must have a value and the values must
  be quoted.

8
Parts and Pieces

• Declaration a parser flag.
• lt?xml version1.0 encodingISO-8859-1
  standaloneno?gt
• Comments between lt!-- and --gt
• Processing Instructions
• lt?cocoon-process typesql?gt
• Entities begin with an ampersand, end in
  semi-colon.
• lt!ENTITY myent My Custom Entity!gt
• lt gt amp quot apos

9
Namespaces

• Namespaces allows developers to include multiple
  elements of the same name in the same document.

ltmath_test xmlnsmtesthttp//www.uark.edu/mathte
st/ xmlnsmmlhttp//www.w3.org/TR/REC-MathMLgt
ltmtestquestion id1gt ltmmlMIgtalt/mmlMIgt ltmm
lMOgt-lt/mmlMOgt ltmmlMIgtblt/mmlMIgt ltmmlMOgtlt/mm
lMOgt lt/math_testgt
10
Document Type Definition

• DTD are used to describe the document element,
  order, and structure.
• lt!-- address.dtd --gt
• lt!ELEMENT address (name, street, city, state,
  postal-code)gt lt!ELEMENT name (title? first-name,
  last-name)gt
• lt!ELEMENT title (PCDATA)gt
• lt!ELEMENT first-name (PCDATA)gt
• lt!ELEMENT last-name (PCDATA)gt
• lt!ELEMENT street (PCDATA)gt
• lt!ELEMENT city (PCDATA)gt
• lt!ELEMENT state (PCDATA)gt
• lt!ELEMENT postal-code (PCDATA)gt
• ? Optional one or more zero or more choice

11
XML Schemas

• XML Schemas use XML syntax, support datatypes
  (even user-defined), and have more expressions.
• lt?xml version"1.0" encoding"UTF-8"?gt
• ltxsdschema xmlnsxsd"http//www.w3.org/2001/XML
  Schema"gt ltxsdelement name"address"gt
• ltxsdcomplexTypegt ltxsdsequencegt
• ltxsdelement ref"name"/gt
• ltxsdelement ref"street"/gt
• ltxsdelement name"postal-codegt
• ltxsdsimpleTypegt ltxsdrestriction
  base"xsdstring"gt ltxsdpattern
  value"0-95(-0-94)?"/gt lt/xsdrestrictiongt
• lt/xsdsimpleTypegt
• lt/xsdelementgt
• lt/xsdschemagt

12
DOM and SAX

• Document Object Model digest the entire
  document and return a tree (of program objects)
  to be accessed by the program.
• Simple API for XML event based model for
  parsing that allows program to catch document
  events as they are needed.

13
Standards

• The Security Assertion Markup Language (SAML) is
  "an XML-based framework for exchanging security
  information.
• Simple Object Access Protocol (SOAP) define an
  XML format for Remote Procedure Call.
• XML-RPC is another less complex method for doing
  RPC.
• The Web Services Description Language (WSDL)
  makes it possible to find a web service and
  interact with it without prior knowledge about
  its design.
• Universal Description, Discovery, and Integration
  (UDDI) protocol defines how to query and publish
  web services with a registry.
• SVG, XSL-FO, MATHML, XForms, OpenOffice.org,
  Extensible Messaging and Presence Protocol
  (XMPP), etc.

14
References

• http//www.xml.com OReilly Network
• http//www.xml.org - OASIS
• http//www-106.ibm.com/developerworks/edu/x-dw-xml
  intro-i.html IBM tutorial on XML, Doug Tidwell
• XML, The Complete Reference. Williamson, 2001
  McGraw-Hill

15
Questions?

• XML Questions?