Last Week. XML (extensible Markup Language) HTML Deficiencies. XML Advantages. Syntax of XML DHTML. Applets. Modifying DOM Event bubbling

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1 XML (extensible Markup Language) Nan Niu CSC Fall 2008 DHTML Modifying DOM Event bubbling Applets Last Week 2 HTML Deficiencies Fixed set of tags No standard way to create new formatting tags Unsuitable for some Web users Interpreting the meaning of the content Better search engines Standard way to represent content/data B2B transactions AJAX Standard way to invoke services Encode function names and arguments XML ( Language for creating markup languages (meta-language) Provides a simple and universal way of storing any textual data Considered a universal data interchange language Examples XHTML VoiceXML (for speech) SOAP WSDL 3 4 XML Advantages Can use a single parser for all XML documents Simplifies application writing Ability to detect syntactic and structural errors via DTD or Schema Independent programs can check document structure Allow standardized data exchange Syntax of XML Two distinct levels Low-level syntax rules Imposed on all XML documents Structural syntactic rules By DTDs (document type definitions) or XML schemas Specify the allowed tags and attributes, the order or appearance, and arrangements Text-based 5 6 1

Interpreting the meaning of the content Better search engines Standard way to represent content/data B2B transactions AJAX Standard way to invoke services Encode function names and arguments XML (www.

2 Low-level Syntax Rules Begin with an XML declaration XML names are used to name elements and attributes (case sensitive) Define a single root element All other elements must be nested inside The root element of XHTML is html Elements with content must have a closing tag Use <element_name /> for those without XML elements (tags) can have attributes Specified with name/value assignments Values must be enclosed by (single or double) quotes Well formed if document adheres to the above rules 7 Typical XML Document Instruction for XML processors <?xml version= 1.0 encoding= ISO ?> <?xml-stylesheet type= text/css href= resume.css?> Elements <tag_name attr1= value1 > </tag_name> Entity references Similar to macros, e.g., (space) Comments  DOCTYPE declaration Identifies the specific document class <!DOCTYPE Catalog SYSTEM cd.dtd > 8 DTD (Document Type Definition) Define a set of structural rules called declarations A set of elements allowed in the document Names of elements, attributes, and entities How and where the elements are to appear Where elements and attributes may occur How elements fit together Determine the XML document structure W3C online validation Valid if document is both well-formed and conforms to its DTD Declaration Keywords!ELEMENT!ATTLIST!ENTITY!NOTATION Used for formal declaration of Processing Instructions (PI) targets (NOT discussed here) 9 10 <!ELEMENT tag-name content> Content Definition: children Declares a new element tag tag-name Must start with letter or - or. with no white spaces May use (OR) to group multiple tag-names content EMPTY: no content is allowed ANY: any content is allowed (defeats the purpose of DTD) #PCDATA: parsable character data; tags inside the text will be treated as markup and entities will be expanded mixed:mixing children with #PCDATA children (see next slide) ( ) Delimits a group A A must occur, one time only A+ A must occur, one or more times A? A may occur zero or one time A* A may occur zero or more times A B Either A or B must occur A, B Both A and B must occur, in that order

be enclosed by (single or double) quotes Well formed if document adheres to the above rules 7 Typical XML Document Instruction for XML processors <?xml version= 1.0 encoding= ISO-8859-1?> <?

3 DTD Example (I) <!ELEMENT a EMPTY> Illegal <a>with content</a> Legal <a></a> or <a /> <!ELEMENT name (#PCDATA)> <name>john</name> <!ELEMENT a (#PCDATA a)+> Mixed <a> text <a>more</a> </a> DTD Example (II) <!ELEMENT (b c d) EMPTY> All of b, c, d are empty tags <!ELEMENT a (b,(c d)+)+> Illegal <a><b /><b /></a> <a><c /><d /></a> Legal <a><b /><c /><d /><b /><d /></a> <!ATTLIST tag-name att-name att-type [default-value]...> Associate name-value pairs with elements att-type CDATA Character data (not parsable) NMTOKEN (or NMTOKENS) Valid XML name (or names) ID Unique identifier IDREF Valid ID of an element NUMBER Enumerates, i.e. explicit set of possible values default-value A value #REQUIRED #IMPLIED Optional #FIXED value Value cannot be changed 15 More DTD Example DTD <!ELEMENT student EMPTY> <!ATTLIST student id ID #REQUIRED name CDATA #REQUIRED gender (male female) #IMPLIED dept CDATA #FIXED cs > XML Document <student id= s01 name= Chris /> 16 Element vs. Attribute Element Data can be considered an independent object Data is related via a parent/child relationship to another piece of information Item needs to occur multiple times Ordering is important Attribute Information that describes other information, such as a status or id Limit values to a predefined list Minimize the file size of target documents Elements Elements vs. Attributes Can have child Elements nested within them Structured and simple data Must appear in the order specified in the schema, but may appear several times. Natural, core content, which would generally appear in every printout/display Attributes Can contain only strings, or lists of strings Used for "atomic" data items Can only appear once in an element Data of secondary importance; often metadata. More detail at pdf 17 (Sub-)Elements represent parts of an Element Properties of an Element 18 3

ELEMENT a (b,(c d)+)+> Illegal <a><b /><b /></a> <a><c /><d /></a> Legal <a><b /><c /><d /><b /><d /></a> 13 14 <!ATTLIST tag-name att-name att-type [default-value].

4 Example: Simple XML App. Example: an XML library application <?xml version="1.0" encoding="iso "?> <!DOCTYPE SYSTEM .dtd > < date= September 20, 2004 > <from>jani</from> <to>tove</to> <subject>reminder</subject> <body>don't forget me this weekend!</body> </ > <!ELEMENT (from,to,subject,body)> <!ELEMENT from (#PCDATA)> <!ELEMENT to (#PCDATA)> <!ELEMENT subject (#PCDATA)> <!ELEMENT body (#PCDATA)> <!ATTLIST date #CDATA #REQUIRED> Write an XML application for storing information about books in a library. Include the following information: title author publisher description type (one of fiction,non-fiction,cookbook,technical) ISBN book id for internal purposes. set of related books flag the best of the related books library.dtd <!ELEMENT library (book+)> <!ELEMENT book (title, author+,publisher,description,related*)> <!ELEMENT title (#PCDATA)> <!ELEMENT author ((firstname, lastname) (lastname, firstname))> <!ELEMENT publisher (#PCDATA)> <!ELEMENT firstname (#PCDATA)> <!ELEMENT lastname (#PCDATA)> <!ELEMENT description (#PCDATA)> <!ELEMENT related EMPTY> <!ATTLIST book bookid ID #REQUIRED type (fiction non-fiction cookbooks technical) #REQUIRED isbn CDATA #REQUIRED> <!ATTLIST related bookref IDREF #REQUIRED> <!ATTLIST related class CDATA #IMPLIED> <!ENTITY [%] name entity-value> % is optional General entities: without % Parameter entities: with % In DTD <!ENTITY threequarters ¾ > <!ENTITY % versionnumber > <!ENTITY version Version %versionnumber; > In XML Document <a> &version; and &threequarters; </a> <!DOCTYPE> <!DOCTYPE rootelement PUBLIC SYSTEM [name] URL> Associate the XML document to a specific document class Root element of the XML document must match rootelement Examples <!DOCTYPE Catalog SYSTEM cd.dtd > rootelement = Catalog url = cd.dtd <!DOCTYPE html PUBLIC -//W3C//DTD HTML 4.01//EN > rootelement = html name = -//W3C//DTD HTML 4.01//EN url = Xerces validator XML Validation java -cp /u/csc309h/lib/xerces.jar:/u/csc309h/lib Validator -v .xml v is very important; otherwise it does not print any errors

ELEMENT from (#PCDATA)> <!ELEMENT to (#PCDATA)> <!ELEMENT subject (#PCDATA)> <!ELEMENT body (#PCDATA)> <!

5 XML Reference Architecture Application XML Processor DOM Sample DOM (Document Object Model) Generates tree-like structure of XML document in memory Programs transverse tree XML File SAX Sample SAX (Simple API for XML) Event based Trigger events as XML is parsed Programs register for events 27 Building Internet Applications ( 1. Develop a data model What information are you gonna store and how will you represent it? 2. Develop a collection of legal transactions on that model, e.g., inserts and updates 3. Design the page flow User interactions; leading to legal transactions An Internet service lives or dies by Steps Implement the individual pages Query the data model, wrap information in XHTML, and return the combined result to the user Intellectually uninteresting (also from an engineering point of view) However, there s where you have a huge range of technology choices 28 5

Develop a data model What information are you gonna store and how will you represent it? 2. Develop a collection of legal transactions on that model, e.g., inserts and updates 3.

DTD Tutorial. About the tutorial. Tutorial

DTD Tutorial. About the tutorial. Tutorial About the tutorial Tutorial Simply Easy Learning 2 About the tutorial DTD Tutorial XML Document Type Declaration commonly known as DTD is a way to describe precisely the XML language. DTDs check the validity