Grenoble Ecole de Management MEDFORIST Workshop XML in Brief

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Grenoble Ecole de ManagementMEDFORIST
WorkshopXML in Brief

• Asuman Dogac
• Middle East Technical University
• Ankara Turkey
• asuman_at_srdc.metu.edu.tr

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XML

• Extensible Markup Language has become the
  universal standard for representing data
• XML started out as a standard data exchange
  format for the Web
• Yet, it has quickly become the fundamental
  instrument in the development of Web-based online
  information services and electronic commerce
  applications
• Almost all recent electronic commerce standards
  are based on XML

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XML

• A subset of SGML (Standard Generalized Markup
  Language) it is defined by World Wide Web
  Consortium
• HTML enables a universal method of displaying
  data XML provides a universal method of
  describing data
• Provides the ability to describe data in an open
  text-based format and deliver it using standard
  http protocol

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XML

• At present, many applications on the Web use XML
  for hosting large amounts of structured and
  semi-structured data
• Representation of information in XML documents
  has been increasing at an astonishing pace
• According to Meta Group, by 2003, about 65 of
  corporate data will be stored in an XML format

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XML The Unifying Technology
XML Messaging
Internet
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Maturity of Web Infrastructure
Technology
Standard
Innovation
Browse the Web
Program the Web
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XML helps address the challenge

• The data is self-describing
• e.g. the meaning of the data is included
  identifiers surround every bit of data,
  indicating what it means
• Far more flexible method of representing
  transmitted information
• e.g. batched orders sent together can have
  different fields and format without breaking apps
  on each end
• Open, standard technologies for moving,
  processing and validating the data
• e.g. the XML parser can automatically parse,
  validate, and feed the information to an
  application, instead of every application having
  to include this functionality

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XML An Example
Data stream in a typical interface
Electronic Commerce, 100, Turban, 25,
Addison-Wesley
Same data stream in XML
ltBOOKgt ltTITLEgt Electronic Commerce
lt/TITLEgt ltQUANTITYgt 100 lt/QUANTITYgt ltAUTHORgtTurb
anlt/AUTHORgt ltPRICEgt25lt/PRICEgt ltPUBLISHERgtAddison
-Wesleylt/PUBLISHERgt lt/BOOKgt
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Mark up (or Tagging)

• XML uses textual markups to define data
• An XML document is comprised of a collection of
  tagged elements each containing a start tag
  (lttagnamegt), an end tag (lt/tagnamegt), and the
  content between the two tags
• Example
• ltPONumbergt 1234ABCD lt/PONumbergt

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Tagging Data in XML

• ltPONumbergt 1234ABCD lt/PONumbergt
• Considering the content only, it is not possible
  to understand what 1234ABCD stands for
• The tag name PONumber intuitively tells that the
  content is a purchase order number
• Similarly, an XML element might be tagged as
  name, gender, birth date, salary, price,
• XML is extensible in the sense that users can
  create their own vocabularies, the tag names are
  neither predefined nor limited

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Adding Structure to data

• Tagged elements may be nested to any depth to
  provide structured data, or may be repeated to
  represent a list of values
• A valid XML document usually contains a single
  root element, which constitutes the top-level of
  nesting
• In other words, a valid XML document represents a
  tree of elements

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Giving Meaning and Structure to Data
Start Tag
Start Tag

• ltPurchaseOrderRequestgt
• ltPONumbergt1234ABCD lt/PONumbergt
• ltPurchaseOrderDategt20030601lt/PurchaseOrderDategt
  
• ltLineItemgt
• ltItemEAN_Identification no9344 /gt
  
• ltQuantityOrderedgt 16 lt/QuantityOrderedgt
  
• ltUnitPricegt 95 ltUnitPricegt
• lt/LineItemgt
• ltLineItemgt lt/LineItemgt
• lt/PurchaseOrderRequestgt

An Element
Another Element
An Attribute
Data
End Tag
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Giving Structure to Data
PurchaseOrderRequest
PurchaseOrderDate
LineItem
PONumber
ItemEAN_Identification
QuantityOrdered
UnitPrice
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Document Type Definition (DTD)

• The principle purpose of the DTD is to declare
  the hierarchy of document elements
• A document type definition defines
• The name of the elements,
• The content model of each element,
• How often and in which order elements may appear,
• If the end-tags can be shortcut,
• The possible presence of attributes and their
  default values,
• The names of the entities

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An Example DTD

• lt?xml version1.0 encodingUTF-8?gt
• lt!DOCTYPE simple
• lt!ELEMENT PurchaseOrderRequest (PONumber,
  PurchaseOrderDate, LineItem)gt
• lt!ELEMENT LineItem (ItemEAN_Identification,
  QuantityOrdered, UnitPrice)gt
• lt!ELEMENT ItemEAN_Identification(PCDATA)gt
• lt!ELEMENT QuantityOrdered (PCDATA)gt
• lt!ELEMENT UnitPrice (PCDATA)gt
• lt! --This is a comment line to state that the
  other elements are skipped --gt ...gt

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DTDs

• A DTD specifies the structure of an XML element
  by specifying the names of its sub-elements and
  attributes
• Sub-element structure is specified using the
  operators
• set with zero or more elements
• set with one or more elements
• ? optional
• or
• All values are assumed to be string values,
  unless the type is ANY in which case the value
  can be an arbitrary XML fragment

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XML Namespaces

• Namespaces are a simple and straightforward way
  to distinguish names used in XML documents, no
  matter where they come from
• The only reason namespaces exist, is to give
  elements and attributes programmer-friendly names
  that will be unique across the whole Internet

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Example

• lthhtml xmlnsxdc"http//www.xml.com/books"
• xmlnsh"http//www.w3.org/HTML/1998/html4"gt
• lthheadgtlthtitlegtBook Reviewlt/htitlegtlt/hheadgt
• lthbodygt ltxdcbookreviewgt ltxdctitlegtXML A
  Primerlt/xdctitlegt
• lthtablegt lthtr align"center"gt
• lthtdgtAuthorlt/htdgtlthtdgtPricelt/htdgt
• lthtdgtPageslt/htdgtlthtdgtDatelt/htdgtlt/htrgt
• lthtr align"left"gt
• lthtdgtltxdcauthorgtSimon St. Laurentlt/xdcauthorgtlt/
  htdgt
• lthtdgtltxdcpricegt31.98lt/xdcpricegtlt/htdgt
• lthtdgtltxdcpagesgt352lt/xdcpagesgtlt/htdgt
• lthtdgtltxdcdategt1998/01lt/xdcdategtlt/htdgt
• lt/htrgt lt/htablegt lt/xdcbookreviewgt lt/hbodygt
  lt/hhtmlgt

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XML Namespaces

• The prefixes are linked to the full names using
  the attributes on the top element.whose names
  begin xmlns.
• The prefixes are just shorthand placeholders for
  the full names
• Those full names are URLs, i.e. Web addresses

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Extensibility in XML

• Anyone can invent new tags and attach a meaning
  to those tags
• But if every user creates its own XML definition
  for describing his data, it is not possible to
  achieve interoperability
• For example, one may prefer to use the tag name
  POR, while another prefers using the tag name
  PurchaseOrderReq
• In other words, a tagged document is not very
  useful without some kind of agreement on the tags
  among inter-operating applications

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Many Efforts for Standardized Tags

• HL7 for healthcare
• RosettaNet for supply chain integration in
  Information Technology and Electronic Components
  domain
• ebXML for eBusiness
• Common Business Library (CBL) for electronic
  catalogs, purchase orders, etc.

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XML Parsers

• A parser takes an XML document and makes its
  structure and content available to an application
  through an API
• There are two main Application Programming
  Interfaces (APIs) for writing parsers
• Document Object Model (DOM) and
• Simple API for XML (SAX)
• Today, many parsers are both DOM and SAX compliant

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XML DOM Parser
A parser validates and makes the data contained
in an XML document available to the application
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XSLT Processor

• Converts an XML document to another form
• An XSL style sheet is a set of transformation
  instructions for converting a source XML document
  to a target document

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Why XML?
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XML vs EDI
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XML vs EDI
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XML vs EDI