XML and XML Applications - Lecture 04 - Web Information Systems (WE-DINF-11912)

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This lecture is part of a Web Information Systems course given at the Vrije Universiteit Brussel.

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XML and XML Applications - Lecture 04 - Web Information Systems (WE-DINF-11912)

  1. 1. 2 December 2005 Web Information Systems XML and XML Applications Prof. Beat Signer Department of Computer Science Vrije Universiteit Brussel http://www.beatsigner.com
  2. 2. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 2 What is XML?  Standardised text format for (semi-)structured information  Meta markup language  tool for defining other markup languages - e.g. XHTML, WML, VoiceXML, SVG, Office Open XML (OOXML)  Data surrounded by text markup that describes the data  ordered labeled tree <note date="2013-10-17"> <to>Reinout Roels</to> <from>Beat Signer</from> <content>Let us discuss exercise 4 this afternoon ...</content> </note>
  3. 3. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 3 ... and What is it Not?  XML is not a programming language  however, it can be used to represent program instructions, configuration files etc.  note that there is an XML application (XSLT) which is Turing complete  XML is not a database  XML is often used to store long-term data but it lacks many database features  many existing databases offer an XML import/export  more recently there exist specific XML databases - e.g. Tamino by Software AG
  4. 4. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 4 XML Example <?xml version="1.0"?> <publications> <publication type="inproceedings"> <title>An Architecture for Open Cross-Media Annotation Services</title> <author> <surname>Signer</surname> <forename>Beat</forename> </author> <author> <surname>Norrie</surname> <forename>Moira</forename> </author> <howpublished>Proceedings of WISE 2009</howpublished> <month>10</month> <year>2009</year> </publication> <publication type="article"> ... </publications>
  5. 5. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 5 Evolution of XML  Descendant of Standard Generalized Markup Language (SGML)  SGML is more powerful but (too) complex  HTML is an SGML application  XML was developed as a “SGML-Lite” version  XML 1.0 published in February 1998  Since the initial XML release numerous associated standards have been published
  6. 6. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 6 Why has XML been so Successful?  Simple  General  Accepted  Many associated standards  Many (freely) available tools
  7. 7. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 7 XML Specification  Provides a grammar for XML documents in terms of  placement of tags  legal element names  how attributes are attached to elements  ...  General tools  parsers that can parse all XML documents regardless of particular application tags  editors and various programming APIs  Specification available at http://www.w3.org/TR/xml/
  8. 8. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 8 XML Tree Document Structure  An XML document tree can contain 7 types of nodes  root node - always exactly one root node  element nodes - element node with optional attribute nodes  attribute nodes - name/value pairs  text nodes - text belonging to an element or attribute  comment nodes  processing instruction nodes - pass information to a specific application via <? ... ?>  namespace nodes
  9. 9. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 9 Well-Formedness and Validity  An XML document is well-formed if it follows the rules of the XML specification  An XML document can be valid according to its Document Type Definition (DTD) or XML Schema  completely self-describing about its structure and content through - the document content - auxiliary files referred to in the document  validity can be checked by a validating XML parser - online validation service available at http://validator.w3.org <ELEMENT publication (title, author+ howpublished?, month, year)> <ELEMENT title (#PCDATA)> <ELEMENT author (surname, forename)> <ATTLIST publication type CDATA> …
  10. 10. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 10 Differences Between XML and HTML  XML is a tool for specifying markup languages rather than a markup language itself  specify “special markup languages for special applications”  XML is not a presentation language  defines content rather than presentation  HTML mixes content, structure and presentation  XML was designed to support a number of applications and not just web browsing  XML documents should be well-formed and valid  XML documents are easier to process by a program
  11. 11. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 11 Differences Between XML and HTML ...  Readability is more important than conciseness  e.g. <tablerow> rather than <tr>  Matching of tags is case sensitive  e.g. start tag <Bold> does not match end tag </BOLD>  Markup requires matching start and end tags  e.g. <p> and </p>  exceptions are special non-enclosing tags e.g. <br/> or <image ... />  Whitespaces in texts are significant
  12. 12. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 12 XHTML  XHTML is a reformulation of HTML to make it an XML application  we accept that HTML is here to stay  improve HTML it by using XML with minimal effort  W3C stopped their work on XHTML <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Vrije Universiteit Brussel</title> </head> <body> ... </body> </html>
  13. 13. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 13 Differences Between XHTML and HTML  Documents must be valid  XHTML namespace must be declared in <html> element  <head> and <body> elements cannot be omitted  <title> element must be the first element in the <head>  End tags are required for non-empty clauses  Empty elements must consist of a start-tag and end-tag pair or an empty element (e.g. <br/>)  Element and attribute names must be in lowercase  Attribute values must always be quoted  Attribute names cannot be used without a value
  14. 14. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 14 XML Technologies XLink XPointer XPath XQuery XSLT
  15. 15. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 15 Overview of XML Technologies  XPath and XPointer  addressing of XML elements and parts of elements  XSL (Extensible Stylesheet Language)  transforming XML documents (XSLT) and XSL:FO  XLink (XML Linking Language)  linking in XML  XQuery (XML Query Language)  querying XML documents  Document Type Definition (DTD) and XML Schema  definition of schemas for XML documents  DTDs have a very limited expressive power  XML Schema introduces datatypes, inheritance etc.
  16. 16. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 16 Overview of XML Technologies ...  SAX (Simple API for XML)  event-based programming API for reading XML documents  DOM (Document Object Model)  programming API to access and manipulate XML documents as tree structures  RDF (Resource Description Framework)  specific XML encoding used by the semantic web
  17. 17. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 17 Document Object Model (DOM)  Defines a language neutral API for accessing and manipulating XML documents as a tree structure  have already seen the HTML DOM model  The entire document must be read and parsed before it can be used by a DOM application  DOM parser not suited for large documents!  Two different types of DOM Core interfaces for accessing supported content types  generic Node interface  node type-specific interfaces  Various available DOM parsers  e.g. JDOM parser specifically for Java
  18. 18. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 18 Document Object Model (DOM) ...  Different DOM levels  DOM Level 1 - concentrates on HTML and XML document models - contains functionality for document navigation and manipulation  DOM Level 2 - supports XML Namespaces - stylesheet object model and operations to manipulate it  DOM Level 3 - specifies content models (DTD and Schemas)
  19. 19. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 19 XPath  Expression language to address elements of an XML document (used in XPointer, XSLT and XQuery)  A location path is a sequence of location steps separated by a slash (/)  various navigation axes such as child, parent, following etc.  have a look at our XSLT/XPath reference document that is available on PointCarré for all the details about XPath  XPath expressions look similar to file pathnames /publications/publication /publications/publication[year>2008]/title //author[3]
  20. 20. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 20 XML Pointer Language (XPointer)  Address points or ranges in an XML document  Uses XPath expressions  Introduces addressing relative to elements  supports links to points without anchors
  21. 21. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 21 XML Linking Language (XLink)  Standard way for creating links in XML documents  Fixes limitations of HTML links where  anchors must be placed within documents  only entire documents or predefined marks (#) can be linked  only one-to-one unidirectional links are supported  XLinks can be defined in separate documents  third-party link (metadata) server  Two types of links  simple links - associate exactly one local and one remote resource (similar to HTML links)  extended links - associate an arbitrary number of resources
  22. 22. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 22 XML Linking Language (XLink) ...  Other XLink features  linking parts of resources  links can be defined at the attribute level  typed links  The Annotea project uses XLink for managing external annotations  for example used in the Amaya Web Browser Annotation in the Amaya Browser
  23. 23. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 23 Simple API for XML (SAX)  Event-based API for XML document parsing  many free SAX parsers available (e.g. Apache Xerces)  Scans the document from start to end  invokes callback methods  Different kinds of events  start of document  end of document  start tag of an element  end tag of an element  character data  processing instruction  SAX parser needs less memory than DOM parser  DOM parser often uses SAX parser to build the DOM tree
  24. 24. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 24 XML Transformations  Developers want to be able to transform data from one format to another  processing of XML documents - XML to XML transformation  post-processing of documents - e.g. XML to XHTML, XML to WML, XML to PDF, ...  The Extensible Stylesheet Language Transformations (XSLT) language can be used for that purpose
  25. 25. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 25 XSLT Processor  The XSLT processor (e.g. Xalan) applies an XSLT stylesheet to an XML document and produces the corresponding output document DTD Source Tree Result Tree Stylesheet Tree DTD XSLT Stylesheet XML Document XHTML, WML, ... DOM Parser XSLT Processor Input Document Output Document
  26. 26. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 26 XSL Transformations (XSLT)  Most important part of XSL  uses XPath for the navigation  XSLT is an expression-based language based on functional programming concepts  XSLT uses  pattern matching to select parts of documents  templates to perform transformations  Most web browsers support XSLT  transformation can be done on the client side based on an XML document and an associated XSLT document
  27. 27. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 27 Example <?xml version="1.0"?> <publications> <publication type="inproceedings"> <title>An Architecture for Open Cross-Media Annotation Services</title> <author> <surname>Signer</surname> <forename>Beat</forename> </author> <author> <surname>Norrie</surname> <forename>Moira</forename> </author> <howpublished>Proceedings of WISE 2009</howpublished> <month>10</month> <year>2009</year> </publication> <publication type="article"> ... </publications>
  28. 28. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 28 XSLT Stylesheet <?xml version="1.0"?> <xsl:stylesheet version="1.0" xmlns:xsl="http.w3.org/1999/XSL/Transform"> ... <xsl:template match="author"> <p> <xsl:value-of select="surname"/> </p> </xsl:template> ... </xsl:stylesheet> <?xml version="1.0" encoding="utf-8"?> <html> ... <p>Signer</p> <p>Norrie</p> ... </html> output
  29. 29. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 29 Other XSLT Statements  <xsl:for-each select="...">  select every XML element of a specified node-set  <xsl:if test="...">  conditional test  <xsl:sort select="..."/>  sort the output  ...  Have a look at the XSLT/XPath reference document that is available on PointCarré  in exercise 4 you will have the chance to implement and execute different XSLT transformations
  30. 30. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 30 XML for Data Interchange  Standard representation to exchange information between different systems  General way to query data from different systems  e.g. via the XML Query (XQuery) language  Connect applications running on different operating systems and computers with different architectures  XML Remote Procedure Call (XML-RPC)  Simple Object Access Protocol (SOAP) which is a successor of XML-RPC and used for accessing Big Web Services - discussed later in the course
  31. 31. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 31 XML Remote Procedure Call (XML-RPC)  XML-RPC specification released in April 1998  Advantages  XML-based lingua franca understood by different applications  HTTP as carrier protocol  not tied to a single object model (as for example in CORBA)  easy to implement (based on HTTP and XML standards)  lightweight protocol  built-in error handling  Disadvantages  slower than specialised protocols that are used in closed networks
  32. 32. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 32 XML-RPC Request and Response POST /RPC2 HTTP/1.0 User-Agent: Java1.2 Host: macrae.vub.ac.be Content-Type: text/xml;charset=UTF-8 Content-length: 245 <?xml version="1.0" encoding="ISO-8859-1"?> <methodCall> <methodName>Math.multiply</methodName> <params> <param> <value><double>128.0</double></value> </param> <param> <value><double>256.0</double></value> </param> </params> </methodCall> HTTP/1.1 200 OK Connection: close Content-Length: 159 Content-Type: text/xml Server: macbain.vub.ac.be <?xml version="1.0" encoding="ISO-8859-1"?> <methodResponse> <params> <param> <value><double>32768.0</double></value> </param> </params> </methodResponse> XML-RPC Request XML-RPC Response
  33. 33. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 33 XML-RPC Error Message HTTP/1.1 200 OK Connection: close Content-Length: 159 Content-Type: text/xml Server: macbain.vub.ac.be <?xml version="1.0" encoding="ISO-8859-1"?> <methodResponse> <fault> <value> <struct> <member> <name>faultCode</name> <value><int>873</int></value> </member> <member> <name>faultString</name> <value><string>Error message</string></value> </member> </struct> </value> </fault> </methodResponse> XML-RPC Response
  34. 34. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 34 XML-RPC Scalar Values XML-Tag Type Corresponding Java Type <i4> or <int> four-byte signed integer Integer <boolean> 0 or 1 Boolean <string> ASCII string String <double> double-precision signed float Double <dateTime.iso8601> date/time Date <base64> base64-encoded binary byte[]
  35. 35. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 35 XML-RPC Composed Values  Complex data types can be represented by nested <struct> and <array> structures XML-Tag Type Corresponding Java Type <struct> A structure contains <member> elements and each member contains a <name> and a <value> element Hashtable <array> An array contains a single <data> element which can contain any number of <value> elements Vector
  36. 36. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 36 OMX-FS XML-RPC Example: GOMES  Object-Oriented GUI for the Object Model Multi- User Extended Filesystem  GOMES is implemented in Java and uses XML-RPC to communicate with the Object Model Multi-user Extended File System (OMX-FS) which was im-plemented in the Oberon programming language XML-RPC
  37. 37. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 37 Framework for Universal Client Access  Generic database interface instead of developing a new interface from scratch for each new device type  The presented eXtensible Information Management Architecture (XIMA) is based on  OMS Java object database - managing the application data  Java Servlet Technology  generic XML database interface - separation of content and representation  XSLT - appropriate XSLT stylesheet chosen based on User-Agent HTTP header field
  38. 38. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 38 XIMA Architecture OMS Java Workspace OMS Java API XML Server HTML Servlet WML Servlet VXML Servlet HTML Browser WML Browser VXML Browser Delegation Builds XML based on JDOM XML + XSLT → Response OM Model Collections, Associations, multiple inheritance and multiple instantiation Main Entry Servlet
  39. 39. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 39 Generic XIMA Interfaces XHTML Interface WML Interface
  40. 40. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 40 Voice Interfaces  Trend for ubiquitous information services  small screens, keyboards etc. often clumsy to use  Sometimes it is necessary to have hand-free interfaces  e.g. while driving or operating a machine  Alternative input modality for visually impaired users  Voice interfaces can be accessed by a regular phone  no new device is required  no installation effort  Improvements in speech recognition and text-to-speech synthesis make automatic voice interfaces more feasible  e.g. for call centers
  41. 41. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 41 VoiceXML Architecture  Various solutions  development: IBM WebSphere Voice Server SDK  deployment: BeVocal Cafe Voice Portal Speech Recogniser Converts voice input into text Speech model Language Analyser Extracts meaning from text Grammar Application Server Gets data (text) from database Application database Speech Synthesiser Generates speech output Pronounciation rules Text Meaning Text Voice Input Voice Output Speech Speech
  42. 42. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 42 VoiceXML Architecture (for XIMA) XIMA Framework Apache Web Server Tomcat OMS Java Database Websphere Voice Server SDK BeVocal Voice Portal
  43. 43. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 43 Basic VoiceXML Concepts  Dialogue  conversational state in a form or menu  form - interaction that collects values for field item variables  menu - presents user with a choice of options - transition to next dialogue based on choice  Input  recognition of spoken input (or recording of spoken input)  recognition of DTMF (dual-tone multi-frequency) input  Output  speech synthesis (TTS)  recorded audio files
  44. 44. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 44 VoiceXML Form Example <?xml version="1.0" encoding="UTF-8"?> <vxml xmlns="http://www.w3.org/2001/vxml" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.w3.org/2001/vxml http://www.w3.org/TR/voicexml20/vxml.xsd" version="2.0"> <form id="drinkForm"> <field name="drink"> <prompt>Would you like to order beer, wine, whisky, or nothing?</prompt> <grammar src="drinks.grxml" type="application/srgs+xml"/> </field> <block> <submit next="http://www.wise.vub.ac.be/drinks.php"/> </block> </form> </vxml>
  45. 45. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 45 VoiceXML Menu Example <?xml version="1.0" encoding="UTF-8"?> <vxml xmlns="http://www.w3.org/2001/vxml" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.w3.org/2001/vxml http://www.w3.org/TR/voicexml20/vxml.xsd" version="2.0"> <menu id="mainMenu"> <prompt> This is the main menu. What would you like to order? <enumerate/> </prompt> <choice next="#foodForm">food</choice> <choice next="#drinkForm">drink</choice> </menu> ... </vxml>
  46. 46. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 46 collections associations objects The database contains #Collections and #Associations Would you like to go to the collections, to the associations, directly to an object or back to the main menu? The database contains the following # associations Choose an association Association 'name' contains #A Would you like to list the members or go back? Association 'name' contains the following # associations Choose a 'domaintype' or a 'rangetype' or say back Object 'oID' is dressed with type 'type' and currently viewed as type 'type'. It contains #Attr, #Links, and #Methods Choose a link or say back The object contains the following # attributes Would you like to hear the attributes, the links or the methods or go back? You can choose among the following links You can choose among the following methods You can view the object as the following types The database contains the following # collections Choose a collection Collection 'name' contains #M Would you like to list the members or go back? Collection 'name' contains the following # members Choose one of the members The database contains #Objects Choose an object or say back Choose a method or say back Choose one of the types or say back The result of the method is Result
  47. 47. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 47 Example: Avalanche Forecasting System Project to provide WAP and voice access
  48. 48. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 48 Other XML Applications  Synchronized Multimedia Integration Language (SMIL)  animations (timing, transitions etc.)  Mathematical Markup Language (MathML)  mathematical notations (content and structure)  Scalable Vector Graphics (SVG)  two-dimensional vector graphics (static or dynamic)  Ink Markup Language (InkML )  digital ink representation (e.g. from digital pen)  Note that XML standards can also be combined  e.g. XHTML+Voice Profile 1.0
  49. 49. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 49 Other XML Applications …  Office Open XML (OOXML)  file format (ZIP) for representing word processing documents, presentations etc. (e.g. *.docx, *.pptx and *.xlsx) - various XML files within these ZIP documents - specific markup languages for different domains (wordprocessingML, presentationML, spreadsheetML, …) <?xml version="1.0" encoding="UTF-8" standalone="yes" ?> <p:sld xmlns:a="http://schemas.openxmlformats.org/drawingml/2006/main" xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships" xmlns:p="http://schemas.openxmlformats.org/presentationml/2006/main"> ... <a:p> <a:r><a:rPr lang="en-GB" dirty="0" smtClean="0" /> <a:t>Other XML</a:t> </a:r> <a:r><a:rPr lang="en-GB" dirty="0" smtClean="0" /> <a:t>Applications ...</a:t> </a:r> <a:endParaRPr lang="en-GB" dirty="0" /> </a:p> ... </p:sld> single slide from a pptx file
  50. 50. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 50 Exercise 4  XML and XSLT transformations
  51. 51. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 51 References  Elliotte Rusty Harold and W. Scott Means, XML in a Nutshell, O'Reilly Media, September 2004  XML and XML Technology Tutorials  http://www.w3schools.com  Masoud Kalali, Using XML in Java  http://refcardz.dzone.com/refcardz/using-xml-java  VoiceXML Version 2.0  http://www.w3.org/TR/voicexml20/  VoiceXML Version 2.0  http://www.w3.org/TR/voicexml20/
  52. 52. October 17, 2014 Beat Signer - Department of Computer Science - bsigner@vub.ac.be 52 References ...  Amaya Web Browser  http://www.w3.org/Amaya/  XML-RPC Homepage  http://www.xmlrpc.com  B. Signer et al., Aural Interfaces to Databases based on VoiceXML, Proc. of VDB6, Brisbane, Australia, 2002  http://www.academia.edu/175464/Aural_Interfaces_to_Da tabases_based_on_VoiceXML  eXtensible Information Management Architecture (XIMA)  http://www.beatsigner.com/xima.html
  53. 53. 2 December 2005 Next Lecture Web Application Frameworks

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