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Objectives Objectives What is XML , in particular in relation to HTML An Introduction to XML and Web Technologies An Introduction to XML and Web Technologies The XML data model and its textual representation XML Documents XML Documents

  1. Objectives Objectives � What is XML , in particular in relation to HTML An Introduction to XML and Web Technologies An Introduction to XML and Web Technologies � The XML data model and its textual representation XML Documents XML Documents � The XML Namespace mechanism Anders Møller & Michael I. Schwartzbach  2006 Addison-Wesley An Introduction to XML and Web Technologies 2 What is XML? Recipes in XML What is XML? Recipes in XML � XML: E x tensible M arkup L anguage � Define our own “ Recipe Markup Language ” � A framework for defining markup languages � Choose markup tags that correspond to concepts in this application domain � Each language is targeted at its own • recipe , ingredient , amount , ... application domain with its own markup tags � No canonical choices � There is a common set of generic tools for • granularity of markup? processing XML documents • structuring? � XHTML : an XML variant of HTML • elements or attributes? � Inherently internationalized and platform • ... independent (Unicode) � Developed by W3C, standardized in 1998 An Introduction to XML and Web Technologies 3 An Introduction to XML and Web Technologies 4 1

  2. Example (1/2) Example (2/2) Example (1/2) Example (2/2) <col l ect i on> <com m ent > <descr i pt i on>Reci pes suggest ed by Jane Dow</ descr i pt i on> Rhubar b Cobbl er m ade wi t h bananas as t he m ai n sweet ener . I t was del i ci ous. <r eci pe i d=" r 117" > </ com m ent > <t i t l e>Rhubar b Cobbl er </ t i t l e> <dat e>W ed, 14 Jun 95</ dat e> <nut r i t i on cal or i es=" 170" f at =" 28% " car bohydr at es=" 58% " pr ot ei n=" 14% " / > <i ngr edi ent nam e=" di ced r hubar b" am ount =" 2. 5" uni t =" cup" / > <r el at ed r ef =" 42" >G ar den Q ui che i s al so yum m y</ r el at ed> <i ngr edi ent nam e=" sugar " am ount =" 2" uni t =" t abl espoon" / > </ r eci pe> <i ngr edi ent nam e=" f ai r l y r i pe banana" am ount =" 2" / > </ col l ect i on> <i ngr edi ent nam e=" ci nnam on" am ount =" 0. 25" uni t =" t easpoon" / > <i ngr edi ent nam e=" nut m eg" am ount =" 1" uni t =" dash" / > <pr epar at i on> <st ep> Com bi ne al l and use as cobbl er , pi e, or cr i sp. </ st ep> </ pr epar at i on> An Introduction to XML and Web Technologies 5 An Introduction to XML and Web Technologies 6 Building on the XML Notation XML Trees Building on the XML Notation XML Trees � Defining the syntax of our recipe language � Conceptually, an XML document is a tree structure • DTD, XML Schema, ... � Showing recipe documents in browsers • node, edge • root, leaf • XPath, XSLT • child, parent � Recipe collections as databases • sibling (ordered), • XQuery ancestor, � Building a Web-based recipe editor descendant • HTTP, Servlets, JSP, ... � ... – the topics of the following weeks... An Introduction to XML and Web Technologies 7 An Introduction to XML and Web Technologies 8 2

  3. An Analogy: File Systems Tree View of the XML Recipes An Analogy: File Systems Tree View of the XML Recipes An Introduction to XML and Web Technologies 9 An Introduction to XML and Web Technologies 10 Nodes in XML Trees Textual Representation Nodes in XML Trees Textual Representation � Text nodes : carry the actual contents, leaf nodes � Text nodes : written as the text they carry � Element nodes : define hierarchical logical � Element nodes : start-end tags groupings of contents, each have a name • < bla ... > ... </ bla > � Attribute nodes : unordered, each associated • short-hand notation for empty elements: < bla / > with an element node, has a name and a value � Attribute nodes : name =“ value ” in start tags � Comment nodes : ignorable meta-information � Comment nodes : <! - - bla - - > � Processing instructions : instructions to specific � Processing instructions : <? target value ?> processors, each have a target and a value � Root nodes : implicit � Root nodes : every XML tree has one root node that represents the entire tree An Introduction to XML and Web Technologies 11 An Introduction to XML and Web Technologies 12 3

  4. Browsing XML (without XSLT) More Constructs Browsing XML (without XSLT) More Constructs � XML declaration � Character references � CDATA sections � Document type declarations and entity references explained later... � Whitespace? An Introduction to XML and Web Technologies 13 An Introduction to XML and Web Technologies 14 Example Well- -formedness formedness Example Well � Every XML document must be well-formed <?xm l ver si on=" 1. 1" encodi ng=" I SO - 8859- 1" ?> <! DO CTYPE f eat ur es SYSTEM " exam pl e. dt d" > • start and end tags must match and nest properly <f eat ur es a=" b" > � • <x><y></y></x> <?m yt ool her e i s som e i nf or m at i on speci f i c t o m yt ool ?> • </z><x><y></x></y> El señor est á bi en, gar çon! Copyr i ght &#169; 2005 • exactly one root element <! [ CDATA[ <t hi s i s not a t ag> ] ] > • ... <! - - al ways r em em ber t o speci f y t he � in other words, it defines a proper tree structure r i ght char act er encodi ng - - > </ f eat ur es> � XML parser : given the textual XML document, constructs its tree representation An Introduction to XML and Web Technologies 15 An Introduction to XML and Web Technologies 16 4

  5. Simpler Alternatives? Applications Simpler Alternatives? Applications S-expressions, 1958: Rough classification: � Data-oriented languages ( col l ect i on � Document-oriented languages ( r eci pe � Protocols and programming languages ( t i t l e " Rhubar b Cobbl er " ) ( dat e " W ed, 14 Jun 95" ) . . . � Hybrids ) ) � XML is defined as a simplified subset of SGML � XML could have been designed simpler... � ... but it wasn’t [end of discussion] An Introduction to XML and Web Technologies 17 An Introduction to XML and Web Technologies 18 Example: XHTML Example: CML Example: XHTML Example: CML <m ol ecul e i d=" M ETHANO L" > <?xm l ver si on=" 1. 0" encodi ng=" UTF- 8" ?> <at om Ar r ay> <st r i ngAr r ay bui l t i n=" i d" >a1 a2 a3 a4 a5 a6</ st r i ngAr r ay> <ht m l xm l ns=" ht t p: / / www. w3. or g/ 1999/ xht m l " > <st r i ngAr r ay bui l t i n=" el em ent Type" >C O H H H H</ st r i ngAr r ay> <head><t i t l e>Hel l o wor l d! </ t i t l e></ head> <f l oat Ar r ay bui l t i n=" x3" uni t s=" pm " > - 0. 748 0. 558 . . . <body> </ f l oat Ar r ay> <h1>Thi s i s a headi ng</ h1> <f l oat Ar r ay bui l t i n=" y3" uni t s=" pm " > - 0. 015 0. 420 . . . Thi s i s som e t ext . </ f l oat Ar r ay> </ body> <f l oat Ar r ay bui l t i n=" z3" uni t s=" pm " > </ ht m l > 0. 024 - 0. 278 . . . </ f l oat Ar r ay> </ at om Ar r ay> </ m ol ecul e> An Introduction to XML and Web Technologies 19 An Introduction to XML and Web Technologies 20 5

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