[PPT] - Ali Kamandi kamandi@ce.sharif.edu Fall 2007 Sharif University of PowerPoint Presentation

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Ali Kamandi

kamandi@ce.sharif.edu Fall 2007 Sharif University of Technology

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eXtensible Markup Language

Metalanguage - used to create other

languages

Has become a universal data-exchange

format

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<bibliography>

<paper ID= "object-fusion"> <authors> <author>Y.Papakonstantinou</author> <author>S. Abiteboul</author> <author>H. Garcia-Molina</author> </authors> <fullPaper source="fusion"/> <title>Object Fusion in Mediator Systems</title> <booktitle>VLDB 96</booktitle> </paper> </bibliography>

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Human-readable

Machine-readable (easy to parse) Standard format for data interchange Possible to validate Extensible

can represent any data can add new tags for new data formats

Hierarchical structure (nesting)

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element

element name Character content Element Content Empty Element

<bibliography> <paper ID="object-fusion"> <authors> <author>Y.Papakonstantinou</author> <author>S. Abiteboul</author> <author>H. Garcia-Molina</author> </authors> <fullPaper source="fusion"/> <title>Object Fusion in Mediator Systems</title> <booktitle>VLDB 96</booktitle> </paper> </bibliography>

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!

<bibliography> <paper ID="object-fusion"> <authors> <author>Y.Papakonstantinou</author> <author>S. Abiteboul</author> <author>H. Garcia-Molina</author> </authors> <fullPaper source="fusion"/> <title>Object Fusion in Mediator Systems</title> <booktitle>VLDB 96</booktitle> </paper> </bibliography>

Attribute name Attribute Value

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"

#$%

Tags properly nested Tag names case-sensitive All tags must be closed

r self-closing

Attributes enclosed in quotes Document consists of a single (root) element

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&

'()*+

Well-Formed:

Structure follows XML syntax rules

Valid:

Structure conforms to a DTD

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,

<DT> <IMG SRC= "greenball.gif" >  <A NAME="object-fusion"></A> Y.Papakonstantinou, S. Abiteboul, H. Garcia-Molina. <A HREF="http://www-cse.ucsd.edu/~yannis/papers/fusion.ps"> "ObjectFusion in Mediator Systems".</A> In <I>VLDB 96.</I> </DT>

HTML confuses presentation with content
No Explicit Structure, Semantics

Author Conference Title

.+*/

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Extensible set of tags

Content orientated Standard Data

infrastructure

Allows multiple output

forms

Fixed set of tags Presentation oriented No data validation

capabilities

Single presentation

XML HTML

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#1#1

XML Document Type Definitions (DTDs): XML Schema

defines structure and data types allows developers to build their own libraries of

interchanged data types

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An XML document may have an optional DTD.

A grammar for XML documents Defines

which elements can contain which other elements which attributes are allowed/required/permitted on

which elements

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Consider an XML document:

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DTD for it might be:

<!DOCTYPE db [ <!ELEMENT db (person*)> <!ELEMENT person (name, age, email)> <!ELEMENT name (#PCDATA)> <!ELEMENT age (#PCDATA)> <!ELEMENT email (#PCDATA)> ]>

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Occurrence Indicator:

Occurrence Indicator One or more Required, repeatable + None, one, or more Optional, repeatable * None or one Optional ? One and only

ne

Required (no indicator)

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21

<!element book paper*> <!element paper (authors, fullPaper?, title, booktitle)> <!element authors author+> <!element author (#PCDATA)>

Character content Authors followed by

ptional fullpaper,

followed by title, followed by booktitle Sequence of 1 or more author Sequence of 0 or more paper

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"

#13%

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&

#13%

<type name="personName">