Extensible Markup Language
Natawut Nupairoj, Ph.D.
Department of Computer EngineeringChulalongkorn University
Outline
Overview. Basic XML Syntax. User-Defined XML Structure
Document Type Definition.
Overview
What is Markup Language ? Old style communication for editing. Between writer and editor. Example:
This are is a mark-up.
We can more text.
add Sometimes, called “Metalanguage”
^
Overview
Family of Computer Markup LanguageStandard Generalized Markup Language
(SGML) Father of them all. Complex.
HyperText Markup Language (HTML) The most popular child. Focus on presentation: for human.
Overview
Extensible Markup Language (XML) Become increasingly popular. Similar to HTML. Focus on describing data
For human and machine.
Extensible Language for creating other languages. Base syntax. User-defined structure.
Example
<?xml version=“1.0” encoding = “UTF-8”?><endangered_species><animal><name language=“English”>Tiger</name><name language=“Latin”>pantera tigris</name><threats><threat>poachers</threat><threat>habitat destruction</threat><threat>trade in tiger bones for traditional Chinese
medicine(TCM)</threat></threats><weight>500 pounds</weight><length>3 yards from nose to tail</length>
...
</endangered_species>
XML Siblings
XML Structure Definition Document Type Definition (DTD). XML Schema.
XML Parser DOM. SAX.
XML-related technologies XSLT. XPath.
XML Components
Element: tag and contentData.
<name>Tiger</name>
XML Components
Attribute: name and value Metadata = Data of Data.
<name language=“English”>Tiger</name>
<name> <language>English</language> <text>Tiger</text></name>
XML Components
Nested element
<animal>
<name language=“English”>Tiger</name>
<name language=“Latin”>Panthera tigris</name>
<weight>500 pounds</weight>
</animal>
XML Components
Empty element
<animal></animal>
<animal />
<picture filename=“tiger.jpg” />
XML Components
Special symbols& for ampersand (&).< for less than sign (<).> for greater than sign (>)." for double quotation (“).' for single quotation or apostrophe (‘).
<weight><500 pounds</weight>
XML Components
Comment
<!–- This is a comment. It can span multiple lines. -->
Basic XML Syntax
All XML files/applications must conform to basic XML syntaxXML declaration is not required (but
recommended).
<?xml version=“1.0”?><endanger_species><name>Tiger</name></endangered_species>
Basic XML Syntax
One and only one root element.
<?xml version=“1.0”?>
<endanger_species>
<name>Tiger</name>
</endangered_species>
Basic XML Syntax
Balanced and matched opening/closing tags.
<?xml version=“1.0”?>
<endanger_species>
<name>Tiger</name>
<picture filename=“tiger.jpg” />
</endangered_species>
Basic XML Syntax
Case-sensitive.
<name>Tiger</Name>
Case-sensitive.
<picture filename=“tiger.jpg” />
User-Defined XML Structure
XML basic syntax The pattern of all XML documents. Does not say about “structure”. Followed basic syntax = well-formed document.
User-Defined XML Structure Which “tags” and “attributes” are allowed. Describe the structure. Followed “structure” = valid document.
Parser and DTD
XML ParserXMLDocument
Yes/No
DTD
Check input using basic syntax and DTD.
Document Type Definition (DTD)
Old-fashioned, simple, but widely used. Internal DTD.<?xml version=“1.0”?><!DOCTYPE endangered_species [...]><endangered_species><animal>...
Document Type Definition (DTD)
External DTD.<?xml version=“1.0” standalone=“no”?>
<!DOCTYPE endangered_species SYSTEM
“http://www.natawut.com/xml/my_xml.dtd”>
<endangered_species>
<animal>
...
Defining Elements
<!ELEMENT endanger_species (animal)>
<!ELEMENT picture EMPTY>
<!ELEMENT endanger_species ANY>
Defining Elements
<!ELEMENT name (#PCDATA)>
<!ELEMENT weight (#PCDATA)>
<!ELEMENT threat (#PCDATA)>
<name language=“English”>Tiger</name>
<weight>500 pounds</weight>
...
Defining Elements
<!ELEMENT animal (name, threats, weight, length, source, picture, subspecies)>
<animal>
<name language=“English”>Tiger</name>
<threats>
<threat>poachers</threat>
</threats>
<weight>500 pounds</weight>
...
</animal>
Defining Elements
<!ELEMENT characteristics ((weight, length) | picture)>
<characteristics>
<weight>500 pounds</weight>
<length>3 yards from nose to tail</length>
</characteristics>
<characteristics>
<picture filename=“tiger.jpg”/>
</characteristics>
Defining Elements
<!ELEMENT animal (name+, threats, weight?, length?, source, picture, subspecies*)>
<!ELEMENT threats (threat, threat, threat+)>
Defining Attributes
<!ELEMENT population (#PCDATA)>
<!ATTLIST population year CDATA #IMPLIES>
<population>445</population>
<population year=“2002”>445</population>
<population year=“year-rabbit”>445</population>
Defining Attributes
<!ELEMENT population (#PCDATA)>
<!ATTLIST population year CDATA #REQUIRED>
<!ELEMENT population (#PCDATA)>
<!ATTLIST population year (2002|2003) #REQUIRED>
<!ELEMENT population (#PCDATA)>
<!ATTLIST population year CDATA ”2002”>
Defining Attributes
<!ELEMENT population (#PCDATA)>
<!ATTLIST population year CDATA #FIXED ”2002”>
Putting Them Together
<!ELEMENT endangered_species (animal*)>
<!ELEMENT animal(name+, threats, weight?, length?, source, picture, subspecies+)>
<!ELEMENT name (#PCDATA)>
<!ATTLIST name language (English | Latin)>
...
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