Extensible Markup Language (XML) Hamid Zarrabi-Zadeh Web Programming Fall 2013

Size: px

Start display at page:

Download "Extensible Markup Language (XML) Hamid Zarrabi-Zadeh Web Programming Fall 2013"

Zoe Pitts
6 years ago
Views:

1 Extensible Markup Language (XML) Hamid Zarrabi-Zadeh Web Programming Fall 2013

2 2 Outline Introduction XML Structure Document Type Definition (DTD) XHMTL Formatting XML CSS Formatting XSLT Transformations JSON

3 3 What is XML? XML is a markup language for encoding documents in a format that is both humanreadable and machine-readable Is designed to transport and store data Emphasizes simplicity, generality, and usability over the Internet Has strong support via Unicode for the languages of the world

4 4 XML History XML is based on SGML, a Standard Generalized Markup Language (ISO 8879:1986) Most of XML comes from SGML unchanged First XML specification draft published in 1996 XML 1.0 became a W3C recommendation in 1998 (fifth edition published in 2008) XML 1.1 published in 2004 (revised in 2006), but is not widely implemented and is rarely used

5 5 XML Example A simple XML example <?xml version="1.0"?> <message> <from>hassan</from> <to>hossein</to> <body>please give me a call!</body> </message>

6 6 XML Example Another example: <?xml version="1.0"?> <books> <book> <title>maktub</title> <author>paulo Coelho</author> </book> <book> <title>never Crashed!</title> <author>microsoft</author> </book> </books>

7 7 XML versus HTML XML and HTML are both markup languages HTML is for displaying data, while XML is for describing data XML syntax differences New tags may be defined at will Tags may be nested to arbitrary depth May contain an optional description of its grammar XHTML is a version of HTML in XML

8 8 XML Markup Languages Lots of new markup languages have been created with XML, including: XHTML RSS for news feeds RDF for describing resources SVG for scalable vector graphics SMIL for describing multimedia for the web MathML for describing mathematical notation

9 9 XML Pros and Cons Pros: software- and hardware-independent simplifying: Cons: sharing data between applications transporting data between different platforms verbosity rather complex parsing and mapping to type systems

10 XML Structure

11 11 XML Tree Each XML document forms a tree structure that starts at the root and branches to the leaves <bookstore> <book category="cooking"> <title lang="en">everyday Italian</title> <author>giada De Laurentiis</author> <year>2005</year> <price>30.00</price> </book> </bookstore>

12 12 XML Tree Example

13 13 XML Tags XML tags are similar to HTML tags but They are case-sensitive All tags must be closed Like HTML tags they must be properly nested All XML documents must have a single root element that contains all other elements This root element can have any name

14 14 XML Attributes XML elements can have attributes Attribute values must be quoted with either single or double quotes <book title="let's party!"> <film name='the "Lost"'/> Attributes have limitations (use with care) Child elements are more flexible alternatives <book> <title>it's me</title> <author>me who</author> </book>

15 Document Type Definitions (DTDs)

16 16 Document Type Definitions Most applications will not be able to deal with general XML documents Instead, they expect documents that have a specific structure This structure can be defined with an XML Document Type Definition (DTD) A DTD specifies the root node's tag name and what it contains

17 17 Valid XML A well-formed XML document which conforms to the rules of a DTD is called a valid XML <?xml version="1.0"?> <!DOCTYPE message SYSTEM "message.dtd"> <message> <from>hassan</from> <to>hossein</to> <body>please give me a call!</body> </message>

18 18 DTD Example A simple DTD for our message example would look like this <!DOCTYPE message [ <!ELEMENT message (from,to,subject,body)> <!ELEMENT from (#PCDATA)> <!ELEMENT to (#PCDATA)> <!ELEMENT subject (#PCDATA)> <!ELEMENT body (#PCDATA)> ]>

19 19 DTD Building Blocks In a DTD we can specify Elements tags and the stuff text between them Attributes information about elements Entities special character <, >, & PCDATA parsed character data Parsed by the XML parser and examined for markup CDATA (unparsed) character data

20 20 Elements There are different ways to declare an element Empty Parsed character data Anything With a specific sequence of children <!ELEMENT br EMPTY> <!ELEMENT p (#PCDATA)> <!ELEMENT x ANY> <!ELEMENT message (from,to,subject,body)>

21 21 Elements with Children Child sequences can be specified using a syntax similar to regular expressions <!ELEMENT picture (polygon+)> <!ELEMENT picture (polygon+)> <!ELEMENT picture (polygon?)> <!ELEMENT polygon (point,point,point+)> <!ELEMENT picture (polygon image)> <!ELEMENT picture (polygon image)*>

22 22 Element Attributes We can also specify which attributes an element has <!ATTLIST element-name attribute-name attribute-type default-value> <!ATTLIST polygon boundary CDATA "black"> <!ATTLIST polygon interior CDATA "white"> <!ATTLIST polygon fill (true false) "true"> <!ATTLIST point x CDATA "0">

23 23 Attribute Value Types Attribute values types can be CDATA - The value is character data (en1 en2..) - The value must be one from an enumerated list ID - The value is a unique id IDREF - The value is the id of another element IDREFS - The value is a list of other ids NMTOKEN - The value is a valid XML name NMTOKENS - The value is a list of valid XML names ENTITY - The value is an entity ENTITIES - The value is a list of entities NOTATION - The value is a name of a notation xml: - The value is a predefined xml value

24 24 Default Attribute Values Default attribute values can be Value - The default value of the attribute #REQUIRED - The attribute value must be included in the element (no default) #IMPLIED - The attribute does not have to be included #FIXED value - The attribute value is fixed

25 25 Entities Entities are variables used to define common text <!ENTITY entity-name "entity-value"> <!ENTITY sut "Sharif University of Technology">... [in XML file:] &sut;

26 26 Example Newspaper <!DOCTYPE newspaper [ <!ELEMENT newspaper (article+)> <!ELEMENT article (headline,byline,body,notes)> <!ELEMENT headline (#PCDATA)> <!ELEMENT byline (#PCDATA)> <!ELEMENT body (#PCDATA)> <!ELEMENT NOTES (#PCDATA)> <!ATTLIST article author CDATA #REQUIRED> <!ATTLIST article editor CDATA #IMPLIED> <!ATTLIST article date CDATA #IMPLIED> <!ATTLIST article edition CDATA #IMPLIED> <!ENTITY publisher "Sample Press"> <!ENTITY copy "Copyright 2013 Sample Press"> ]>

27 27 XML Schema XML Schema is an XML-based alternative to DTD Main differences to DTDs XML schemas use XML syntax XML schemas support data types XML schemas are extensible

28 28 Schema Example <?xml version="1.0"?> <xs:element name="message"> <xs:complextype> <xs:sequence> <xs:element name="to" type="xs:string"/> <xs:element name="from" type="xs:string"/> <xs:element name="subject" type="xs:string"/> <xs:element name="body" type="xs:string"/> </xs:sequence> </xs:complextype> </xs:element>

29 XHTML

30 30 XHTML XHTML is a version of HTML that is proper XML XHTML 1.0 released in 2000 Because it is XML, it is defined using a DTD The html tag must have an xmlns attribute <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" " transitional.dtd"> <html xmlns=" <body> </body> </html>

31 31 XHTML versus HTML XHTML and HTML have mostly the same tags Main differences have to do with XML syntax All tags must be closed Empty tags must also be closed Elements must be properly nested Tag names must be lowercase Attribute values must be quoted Attributes must have values <input type="checkbox" checked="checked" /> <input type="text" readonly="readonly" /> The id attribute replaces the name attribute

32 Formatting XML

33 33 CSS Formatting Formatting information can be added to XML documents using CSS This works by adding a reference to a CSS stylesheet in the XML document header <?xml version="1.0"?> <?xml-stylesheet type="text/css" href="msg.css"?> <message> <from>hassan</from> <to>hossein</to> <body>please give me a call!</body> </message>

34 34 CSS Example The :before and :after CSS pseudo-elements can be very useful here from { display: block; padding: 10px; } from:before { content: "From: "; font-weight: bold; }

35 35 XSLT Transformations Formatting XML with CSS is not the most common method W3C recommends using XSLT instead XSLT (extensible Stylesheet Language Transformation) is a language for transforming XML documents into other XML documents To display XML on the web, we could use XSLT to convert our XML document into an XHTML document

36 36 XSLT Example <?xml version="1.0"?> <html xsl:version="1.0" xmlns:xsl=" xmlns=" <body> <xsl:for-each select="messages/message"> <div style="padding:10px; margin:10px> <div><b>from</b>: <xsl:value-of select="from"/></div> <div><b>to</b>: <xsl:value-of select="to"/></div> <div><xsl:value-of select="body"/></div> </div> </xsl:for-each> </body> </html>

37 JSON

38 38 What is JSON? JSON stands for JavaScript Object Notation It is a lightweight text-data interchange format, commonly used as an alternative to XML JSON is smaller, faster and easier to parse Although JSON uses JavaScript syntax, it is still language and platform independent.

39 39 JSON Examples { } "message": { "from": "Hassan", "to": "Hossein", "body": "Please give me a call!" } { } "books": [ {"title": "Maktub", "author": "Paulo Coelho"}, {"title": "Crashed!", "author": "Microsoft"} ]

40 40 Summary XML is used to describe data DTDs and Schemas can be used to define valid documents XML can be formatted with CSS and XSLT XHTML is a version of HTML which is proper XML JSON is a good alternative to XML

41 41 References W3Schools Internet Programming by Pat Morin Wikipedia

markup language carry data define your own tags self-descriptive W3C Recommendation

markup language carry data define your own tags self-descriptive W3C Recommendation XML intro What is XML? XML stands for EXtensible Markup Language XML is a markup language much like HTML XML was designed to carry data, not to display data XML tags are not predefined. You must define