Internet Technology 1 Presentation 10: XML technologies

Internet Technology 1

Presentation 10:

XML technologies

Ingeniørhøjskolen i ÅrhusSlide 2 af 34

Outline

• W3C & heritage of XML• XML Markup & Namespaces• DTD’s• XML Schemas• DOM/SAX


W3C & the legacy of XML

• World Wide Consortium– Founded 1994 to lead the WWW into the future– For standardizations on the Internet– First Chairman: Sir Tim Berners-Lee– Run by Chairman, Director & Staff– Boards of members submits proposals and work to formulate– Ensures standardization of WWW technologies

• Like: XHTML, XML, XSL, CSS, SOAP, WAP etc.• Members: Microsoft, IBM, SUN, Oracle

– http://www.w3c.org


SGML

• Standard Generalized Markup Language (ISO 8879:1986 SGML)

• ISO-standard technology for defining generalized markup languages for documents

• Original SGML, which was accepted in October 1986

• Based on Generalized Markup Language (GML)

• GML was developed in the 1960s by Charles Goldfarb, Edward Mosher and Raymond Lorie

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XML markup

• eXtended Markup Language• XML based on SGML (subset of)• Like SGML for structure not layout (as HTML)• XML targets the Internet – but is also being used

for application exchange formats (Open Office, XMI) – CSVs

• XML is an W3C Recommendation– http://www.w3.org/TR/REC-xml

• Structure decided by DTD or Schema (more later)• Wide spread support for XML (hype)


Examples of XML usage

• GUI for “thin” clients– XHTML– WML (we shall look closer at this shortly)

• Inter-process communication– SOAP– BizTalk– ebXML

• Databases– XML Databases– XQuery– XLink, XPointer

• Representation / exchange of data– XMI (UML diagrams exchange format)– MathXML– CML– Proprietary

• Example: EPJ XML –good thing when every danish county makes its own• Easy to comprehend due to the nature of XML• Open office


Presenting XML documents

• Examples fetched from DEITEL• First we will look at a standalone XML document

and its components (elements)– Note: XML document needs to be Well formed (must

be syntactically correct)

• Please go to http://www.w3schools.com/default.asp to see more in-depth examples of XML usage


Article.xml

1 <?xml version = "1.0"?>2 3 4 5 6 <article>7 8 <title>Simple XML</title>9 10 <date>September 19, 2001</date>11 12 <author>13 <firstName>Tem</firstName>14 <lastName>Nieto</lastName>15 </author>16 17 <summary>XML is pretty easy.</summary>18 19 <content>Once you have mastered XHTML, XML is easily20 learned. You must remember that XML is not for21 displaying information but for managing information.22 </content>23 24 </article>

Element article is the root element.

Elements title, date, author, summary and content are child elements of article.

Element author is a “container element” contains Childs, firstName and lastName


Browser displaying XML (unformatted)

IE5.5 displaying article.xml.


Small “stop up” exercise 1

• We will do some small common exercises.• Use 5 min. to this exercise:• Setup a XML document, containing data about

your merits at IHA and other institutions– Incl. “group of subjects” to which you have participated

and your possible trainee period– The courses might have a name, a code, a type, a

course holder, type of assessment, and other topics you find of relevance. Start with 2-3 courses

– Your course gradings how do they relate to the courses and what are they?


Use of XML Namespaces

• XML namespaces used to avoid naming conflicts• When several different elements are involved• <book> isn't always a book• Keyword ”xmlns”• Remember xmlns is nothing more than organizing

names in spaces.


Namespace.xml

1 <?xml version = "1.0"?>2 3 4 5 6 <text:directory xmlns:text = "urn:deitel:textInfo"7 xmlns:image = "urn:deitel:imageInfo">8 9 <text:file filename = "book.xml">10 <text:description>A book list</text:description>11 </text:file>12 13 <image:file filename = "funny.jpg">14 <image:description>A funny picture</image:description>15 <image:size width = "200" height = "100"/>16 </image:file>17 18 </text:directory>

Keyword xmlns creates two namespace prefixes, text and image.

URIs (Uniform Resource Identifiers) ensure that a namespace is unique.

Attribute


Defaultnamespace.xml

1 <?xml version = "1.0"?>2 3 4 5 6 <directory xmlns = "urn:deitel:textInfo"7 xmlns:image = "urn:deitel:imageInfo">8 9 <file filename = "book.xml">10 <description>A book list</description>11 </file>12 13 <image:file filename = "funny.jpg">14 <image:description>A funny picture</image:description>15 <image:size width = "200" height = "100"/>16 </image:file>17 18 </directory>

Default namespace.

Element file uses the default namespace.

Element file uses the namespace prefix image.


Stop up exercise 2

• Use Namespace(s) in your XML document (from s.u. exc. 1)


DTDs

• Document Type Definition• Extended Backus-Naur Form• Defines how an XML document is structured

– Required elements

– Nesting of elements

– Does not define types or behaviour

• If DTD is used – some parsers can decide if XML document is “valid” – which is more than just “well formed”


Letter.dtd1 2 3 4 <!ELEMENT letter ( contact+, salutation, paragraph+, 5 closing, signature )>6 7 <!ELEMENT contact ( name, address1, address2, city, state,8 zip, phone, flag )>9 <!ATTLIST contact type CDATA #IMPLIED>10 11 <!ELEMENT name ( #PCDATA )>12 <!ELEMENT address1 ( #PCDATA )>13 <!ELEMENT address2 ( #PCDATA )>14 <!ELEMENT city ( #PCDATA )>15 <!ELEMENT state ( #PCDATA )>16 <!ELEMENT zip ( #PCDATA )>17 <!ELEMENT phone ( #PCDATA )>18 <!ELEMENT flag EMPTY>19 <!ATTLIST flag gender (M | F) "M">20 21 <!ELEMENT salutation ( #PCDATA )>22 <!ELEMENT closing ( #PCDATA )>23 <!ELEMENT paragraph ( #PCDATA )>24 <!ELEMENT signature ( #PCDATA )>

The ELEMENT element type declaration defines the rules for element letter.

The plus sign (+) occurrence indicator specifies that the DTD allows one or more occurrences of an element. (2 contacs in our example)

The contact element definition specifies that element contact contains child elements name, address1, address2, city, state, zip, phone and flag— in that order.

#CDATA Unparsed character#PCDATA Parsed character


Letter.dtd

1 2 3 4 <!ELEMENT letter ( contact+, salutation, paragraph+, 5 closing, signature )>6 7 <!ELEMENT contact ( name, address1, address2, city, state,8 zip, phone, flag )>9 <!ATTLIST contact type CDATA #IMPLIED>10 11 <!ELEMENT name ( #PCDATA )>12 <!ELEMENT address1 ( #PCDATA )>13 <!ELEMENT address2 ( #PCDATA )>14 <!ELEMENT city ( #PCDATA )>15 <!ELEMENT state ( #PCDATA )>16 <!ELEMENT zip ( #PCDATA )>17 <!ELEMENT phone ( #PCDATA )>18 <!ELEMENT flag EMPTY>19 <!ATTLIST flag gender (M | F) "M">20 21 <!ELEMENT salutation ( #PCDATA )>22 <!ELEMENT closing ( #PCDATA )>23 <!ELEMENT paragraph ( #PCDATA )>24 <!ELEMENT signature ( #PCDATA )>

The ATTLIST element type declaration defines an attribute (i.e., type) for the contact element.

Keyword #IMPLIED specifies that if the parser finds a contact element without a type attribute, the parser can choose an arbitrary value for the attribute or ignore the attribute and the document will be valid.

Flag #PCDATA specifies that the element can contain parsed character data (i.e., text).

See letter.xml next page


Letter.xml

1 <?xml version = "1.0"?>2 3 4 5 6 <!DOCTYPE letter SYSTEM "letter.dtd">7 8 <letter>9 10 <contact type = "from">11 <name>John Doe</name>12 <address1>123 Main St.</address1>13 <address2></address2>14 <city>Anytown</city>15 <state>Anystate</state>16 <zip>12345</zip>17 <phone>555-1234</phone>18 <flag gender = "M"/>19 </contact>20 21 <contact type = "to">22 <name>Joe Schmoe</name>23 <address1>Box 12345</address1>24 <address2>15 Any Ave.</address2>25 <city>Othertown</city>26 <state>Otherstate</state>27 <zip>67890</zip>28 <phone>555-4321</phone>29 <flag gender = "M"/>30 </contact>31


Letter.xml

Program Output

32 <salutation>Dear Sir:</salutation>33 34 <paragraph>It is our privilege to inform you about our new35 database managed with XML. This new system allows36 you to reduce the load of your inventory list server by37 having the client machine perform the work of sorting38 and filtering the data.</paragraph>39 <closing>Sincerely</closing>40 <signature>Mr. Doe</signature>41 42 </letter>

http://msdn.microsoft.com/archive/default.asp?url=/archive/en-us/samples/internet/welcome.asp


Program Output

http://msdn.microsoft.com/archive/default.asp?url=/archive/en-us/samples/internet/welcome.asp Or from http://kurser.iha.dk/eit/net1/iw3_htp_3e_examples/ch20_XML/xml_validator.exe


Stop up exercise 3

• Take 5 minutes:• Setup a DTD, that confirms to your xml

document educations.xml and extend the xml document with DTD information


XML Schema

• DTD works OK – but– Is in Ex. Backus-Naur Form – why not use XML to describe?– Cannot declare a type to of an element – <amount>hundrede kr</amount>

• Could give problems

– Several other problems

• W3C XML Schema– Use XML to describe the structure of XML documents …– Possible to give type information to XML definitions

• Not supported by all parsers yet• Will live besides DTDs for a while


Book.xsd1 <?xml version = "1.0"?>2 3 4 5 6 <xsd:schema xmlns:xsd = "http://www.w3.org/2000/10/XMLSchema"7 xmlns:deitel = "http://www.deitel.com/booklist"8 targetNamespace = "http://www.deitel.com/booklist">9 10 <xsd:element name = "books" type = "deitel:BooksType"/>11 12 <xsd:complexType name = "BooksType">13 <xsd:element name = "book" type = "deitel:BookType"14 minOccurs = "1" maxOccurs = "unbounded"/>15 </xsd:complexType>16 17 <xsd:complexType name = "BookType">18 <xsd:element name = "title" type = "xsd:string"/>19 </xsd:complexType>20 21 </xsd:schema>

Namespace prefix.

Element element defines an element to be included in the XML document structure.

Attributes name and type specify the element’s name and data type, respectively.

Element complexType defines an element type that has a child element named book.

Attribute minOccurs specifies that books must contain a minimum of one book element.

The resulting namespace.


Book.xsd

1 <?xml version = "1.0"?>2 3 4 5 6 <xsd:schema xmlns:xsd = "http://www.w3.org/2000/10/XMLSchema"7 xmlns:deitel = "http://www.deitel.com/booklist"8 targetNamespace = "http://www.deitel.com/booklist">9 10 <xsd:element name = "books" type = "deitel:BooksType"/>11 12 <xsd:complexType name = "BooksType">13 <xsd:element name = "book" type = "deitel:BookType"14 minOccurs = "1" maxOccurs = "unbounded"/>15 </xsd:complexType>16 17 <xsd:complexType name = "BookType">18 <xsd:element name = "title" type = "xsd:string"/>19 </xsd:complexType>20 21 </xsd:schema>

A BookType has an Element named Title of Type “xsd:string” – which is defined at “http://www.w3.org/2000/10/XMLSchema”



Stop up exercise 4

• Take a 5 minutes discussion to your neighbor about how to replace the DTD with a Schema


How to use XML?

• Need a parser (or a parser API) to access XML (as with CSV)• Two commonly used methods:

– DOM (Document Object Model)• W3C Recommendation• Makes a tree structure representation of an XML document in memory

– SAX (Simple API for XML)• Supported by diff. vendors• Parses document line by line and sends events to subscribers• Needs to parse every time access to XML document is needed

• DOM is better for– Slow to load XML document (need all)– Quick access to random read or update of XML (like WWW browser - BOM)– Requires a lot of memory (need to hold entire XML in mem)

• SAX is better for– Applications subscribing to certain parts of XML (event subscription)– Slow for random access to XML document (must parse every time)

• Think at a XML documents as a kind of persistent data (“a database”)


What is DOM

• DOM: Document Object Model– http://www.w3.org/TR/2003/REC-DOM-Level-2-HTML-

20030109/

• W3C definition:– Standard for accessing structured documents– Core DOM used with XML– HTML DOM used with HTML– Representation of an object as an object tree structure – Provides a uniform interface for programming and scripting

languages– API’s available for JavaScript, Java, C++, C# etc.


DOM Tree Structure

• Tree structure of an XML document (left)• … or HTML (right) document

… table

tbody

…

… …

tr trtr

td tdtd

tekst

<table> <tbody> <tr> <td> tekst </td>….


Example – using DOM on Article.xml

• We have looked at Article.xml• We Will:

– Look at the Article.xml document again

– Look at the Tree Structure formed by loading it into a DOM

– Use JavaScript to work on it


1 <?xml version = "1.0"?>2 3 4 5 6 <article>7 8 <title>Simple XML</title>9 10 <date>September 19, 2001</date>11 12 <author>13 <firstName>Tem</firstName>14 <lastName>Nieto</lastName>15 </author>16 17 <summary>XML is pretty easy.</summary>18 19 <content>Once you have mastered XHTML, XML is easily20 learned. You must remember that XML is not for21 displaying information but for managing information.22 </content>23 24 </article>

XML document – Article.XML


DOM Methods

firstName

lastName

contents

summary

author

date

title

article

Tree structure for article.xml.


DOMExample.html

1 <?xml version="1.0"?>2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"3 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">4 <html xmlns="http://www.w3.org/1999/xhtml">5 6 7 8 9 <head>10 <title>A DOM Example</title>11 </head>12 13 <body>14 15 <script type = "text/javascript" language = "JavaScript">16 63 </script>64 65 </body>66 </html>

Retrieve the root node’s first child node (i.e., title) using property firstChild.

Property parentNode returns a node’s parent node.


Program Output


Tools

• XML-Spy: www.xml-spy.com• Sun’s Stylus Studio: www.stylusstudio.com • Others:

– API’s for programmatic access


Formatting XSL & CSS

• XML is only content – no formatting

• Possible to transform the data to XHTML (or other) using JavaScript og server-side

• The W3C ideal is using CSS or XSL – eXtensible Style Sheets

• CSS is most common today– but XSL has more features


The 3 Main Technologies of XSL

• XSLT, a language for transforming information

• XSL or XSL-FO, a language for formatting information

• XPath, a language for defining parts of an XML document and accessing them

• Each of these elements could fill an entire class.• We will be dealing with them in a later course

Documents

Internet Technology 1 Presentation 10: XML technologies