XML eXtensible Markup Language An Introduction

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XML eXtensible Markup Language An
Introduction

• Marion A. Royal
• GSA
• Office of Governmentwide Policy

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Preface
Before adopting XML, one must first decide which
problem you are trying to solve. Next, you must
make sure that you understand the architecture to
determine the appropriate place to use XML. If
you are not moving data between systems, dont
force feed XML just for the sake of it. Ken
Wheeler DISA DII COE
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A Little History

• HTML has opened a channel for online information
  exchange. Unfortunately, it has become a
  limiting factor for us.
• XML is not really the new kid on the block. It
  is a subset of SGML, which has been in use for a
  decade or so.

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Limitations of HTML

• Limited number of tags.
• Browsers are forgiving.
• Browser developers may be tempted to add new tags
  that only work with their product.
• Cant customize layout from the clients side.
• Product comparison

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Origin of XML

• World Wide Web Consortium (W3C) XML Working
  Group
• Work begun in 1996
• Version 1.0 Recommendation released on 10 Feb 98
• Second Edition on 6 Oct 00http//www.w3.org/TR

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Advantages of XML

• Data ReusabilitySingle Source - Multiple output
• Targeted RetrievalDocuments authored by, not
  about
• Flexibility
• Accessibility
• Portability

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XML and HTML

• HTML tells how data should look, but XML tells
  you what it means.
• XML applies context to the data and separates
  data content from data presentation.
• XML provides a hierarchical structure.
• However, XML is not designed to replace HTML.

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XML and EDI

• Not a replacement for EDI
• Small and Medium sized Enterprises may deploy XML
  before looking to EDI
• XML developers are using the lessons learned from
  EDI

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US - Emerging Trends Compared
USA 2 x Rest of World
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Design Goals for XML

• 1. XML shall be straightforwardly usable over the
  Internet.
• 2. XML shall support a wide variety of
  applications.
• 3. XML shall be compatible with SGML.
• 4. It shall be easy to write programs which
  process XML documents.
• 5. The number of optional features in XML is to
  be kept to the absolute minimum, ideally zero.
• 6. XML documents should be human-legible and
  reasonably clear.
• 7. The XML design should be prepared quickly.
• 8. The design of XML shall be formal and
  concise.
• 9. XML documents shall be easy to create.
• 10. Terseness in XML markup is of minimal
  importance.

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Structuring Data

• Comma delimitedMarion,A.,Royal,GSA,202.208.4643
• Semi-Structured
• fname/Marion/initial/A./lname/Royal/agency/GSA/pho
  ne/202.208.4643

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Sample XML Fragment
ltNAMEgt ltFIRSTgtMarionlt/FIRSTgt ltMIDDLEgtA.lt/MIDDLEgt
ltLASTgtRoyallt/LASTgtlt/NAMEgtltAGENCYgtGSAlt/AGENCYgt
ltPHONEgt ltAREA_CODEgt202lt/AREA_CODEgt ltPREFIXgt208lt/
PREFIXgt ltNUMBERgt4643lt/NUMBERgtlt/PHONEgt
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Other XML TechnologiesValidation

• DTD Document Type Definition
• Defines the permissible tagging structure for a
  document
• Borrowed from SGML
• example
• XML Schemas
• Will ultimately replace DTDs, more flexible
• Developed specifically to validate XML
• example

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Document Type Definitions

• Defined by its elements
• A DTD is a series of definitions for element
  types, attributes, entities and notations.
• Set of rules which may be very stringent or
  flexible
• XML Documents do not require DTDs
• DTDs may be part of the document or may be
  externally referenced.

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DTD Example
lt!ELEMENT NAME (FIRST,MIDDLE,LAST)gtlt!ELEMENT
FIRST (PCDATA)gtlt!ELEMENT MIDDLE
(PCDATA)gtlt!ELEMENT LAST (PCDATA)gtlt!ELEMENT
AGENCY (PCDATA)gtlt!ELEMENT PHONE
(AREA_CODE,PREFIX,NUMBER)gtlt!ELEMENT
AREA_CODE(PCDATA)gt lt!ELEMENT PREFIX(PCDATA)gt lt!E
LEMENT NUMBER(PCDATA)gt
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W3C XML Schema

• Part 1 StructuresDescribe the relationships
  and semantics of the data.
• Part 2 DatatypesDefine the primitive and
  generated datatypes.

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Other XML TechnologiesDisplay

• CSS - Cascading Style Sheets
• Pro Easily define display properties of an XML
  element
• Con Not very powerful
• Web browser only
• example
• XSL Extensible Stylesheet Language
• Pro can transform XML into any other markup
  language. (powerful)
• Con more complicated to use
• example

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Cascading Style Sheets
name display block font-family
Arial font-size 14pt margin-top
20px phone color cc0000 font-style
italic font-size 16pt position
relative left 10px
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XSLExtensible Stylesheet Language

• Controls presentation of data
• Can enable multiple types of devices to view your
  content
• Can convert between different XML formats (useful
  in data interchange)
• Learning Stylesheets is like finding the square
  root of pi with Roman Numerals Walker White -
  Oracle

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XML and HTML
Data in XML
StyleSheets
Layout in HTML
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XSL Transformations
XML
XSL Transformation
Plain Text
XML
WML
PDF
SGML
HTML
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XML Deployment

• System to System
• Application to Application
• Client to Server

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Technology Leaders Driving XML
Application Integration
Application Integration
Native XML Applications
Native XML Applications
Content Management
Content Management
e-Commerce
e-Commerce
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Sounds Good, Right?

• Not so fast, My Friend

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The Tower of Babel
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ebXML Development
Core Technology Standards
IT Supply Chain
ASC X.12 EDI
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Federal CIO XML WG

• Chartered in June 2000
• Enterprise Emerging IT Interoperability
  Committee (EIEITC)
• XML.GOV
• Mail List

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Data is only valuable...
when it can be transformed into useful
information and then into knowledge. -Bryan
Caporlette - Sequoia Software
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References

• HttpXML.GOV
• http//www.w3.org
• http//www.xml.com
• http//www.ibm.com/developer/xml/
• http//biztalk.com/
• http//www.oasis-open.org/ marion.royal_at_gsa.go
  v 202.208.4643