xml bradsher 4-30-03
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XMLeXtensible Markup Language
Charles A. Bradsher
Defense Technical Information Center
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eXtensible Markup Language
World Wide Web Consortium (W3C)
I.E. Legal XML QueryXML, Voice XML
Promotes business to business exchange (B2B)
Does not describe Formatting -Its about content
Uses any kind of information any kind of content
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What is XML?
eXtensible - By applying Identifiers for
elements of information in a neutral way,
stored in a neutral form, independent ofsystems, devices and applications.
Markup - For adding information to adocument relating to its structure and/or
content.
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What is XML?
Language - A standard methodology with
formal syntax..However
XML is not a language but a toolkit fordeveloping or defining languages
A common syntax for expressing structure
in data
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How are SGML, HTML & XML
Related? Standard Generalized Markup Language
HTML is an application of SGML
XML is a subset of SGML
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Tags
Mrs. Air
Documents
1234 Concord Street Anytown
VA
45678
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Content
Mrs. Air
Documents
1234 Concord Street Anytown
VA
45678
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XML is Tags and Content
A Hierarchical Data RepresentationA Tree Structure Data
Representation
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Why Do We Need XML?
Interoperability
Info can be separated from the way it is
presented
Information can be presented in a variety of
ways depending on the device the end user
has.
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Why Do We Need XML?
Future Web developments hinge on the use
of XML W3C
Dependence on a single, inflexible document type
(HTML) which was being abused for task for which it
was never designed
SGML was too complex to fill the gap
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HTML vs. XML
Mrs. Air Documents
1234 Concord Street
Anytown, VA 45678
Mrs. Air Documents
1234 Concord Street Anytown, VA 45678
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HTML vs. XML
Mrs.
Air
Documents
1234 Concord Street Anytown
VA
45678
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HTML vs. XML
Mrs. Air Documents
1234 Concord Street
Anytown, VA 45678
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Mrs Air Documents
1234 Concord Street
Anytown, VA 45678
Mrs AirDocuments1234 Concord Street
Anytown, VA 45678
OMB 24 t
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OMBs 24 e-governmentInitiatives
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Why is XML Important?
Does not need a specific application
Perpetual preservation of Information
Could be future standardized mechanism forthe exchange of data
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How Does It Work?
XML Parser
XML Processor
XML does not provide an application
programming interface (API). ( Just passes
data to the application)
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What is a DTD?
DTD - Document Type Definition
A set of syntax rules for tags
What tags you can use in a document
Where the tags appear
Which tags can appear inside other tags
A set of constraints for documents
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DTD vs. Schema
DTD content models are closed and cant reflect the
openness XML supports.
DTD doesnt support data types beyond the 10primitive types.
It cant express rich data types allowed in XML
Schema
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Schema
Microsoft proposed an alternative approachto DTDs called schema
Like DTDs, schema provide the rules of adocument and indicate what tags areused.
Unlike DTDs, schema can define datatypes.
Designed to replace and amplify DTDs
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Schema
date)>
quantity CDATA #REQUIRED>
month CDATA #REQUIRED
year CDATA #REQUIRED >
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Schema
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Schema
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Schema
Example
A DTD might have a tag designated as
, but the content contained within thattag could be a number or a character string. A
schema would force you to enter a number.
DTD Schema
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Stylesheets
Provides hints and algorithms for rendering or
transforming the data in the XML document.
XSLT Extensible Stylesheet Language cantransform from one XML format to another
including HTML or plain text.
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For More XML Information:
For basic Information on XML:
http://www.xml.org/xml/resources_focus_b
eginnerguide.shtml W3C: http://www.w3.org/
Robin Cover's extensive list of online
reference material and links to software:http://xml.coverpages.org/
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QUESTIONS?