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XML Extensible Markup Language

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Title: XML Extensible Markup Language


1
XML (Extensible Markup Language)
2
Introduction
  • XML
  • The Extensible Markup Language (XML) is a
    document processing standard proposed by the
    World Wide Web Consortium (W3C), which is related
    to Standard Generalised Markup Language (SGML).
  • Possible to search, sort, manipulate and render
    XML using Extensible Markup Language (XSL)
  • Highly portable
  • Files end in the .xml extension

3
From HTML to XML..
  • HTML major drawback information loses its
    structure when translated into HTML
  • HTML is a presentation-oriented markup language,
    so information embodied in it is difficult to
    process
  • Information and knowledge servers are overloaded
    because have to search information and perform
    format processing
  • Servers often answer the same request many times
    if users request several views on the same data

4
From HTML to XML..
  • HTML
  • Lacks extensibility cant create tags or
    attributes to parameterise or semantically
    qualify data
  • Lacks structure does not support the
    specification of deep structures needed to
    represent database schemas or object-oriented
    hierarchies
  • Lacks validation does not support language
    specification that lets applications check
    imported datas structural validity

5
XML..
  • XML is not for displaying information but for
    managing information.
  • Working group of World Wide Web Consortium (W3C)
    created XML as a standard for creating markup
    languages.
  • Designed it for distributing structured
    documents over the web
  • A kind of light SGML (Standard General Markup
    Language) simplified to meet Web requirements
  • Unlike HTML, XML lets users
  • Extract data from a document
  • Define their own tags and attributes
  • Define data structures and nest document
    strcutures to any complexity level
  • Make applications that validate a documents
    structure. Any XML document can contain an
    optional description of its grammar for use by
    applications that perform structural validation

6
XML..
  • The problem that XML helps us to solve is how to
    transfer data between servers, or between the
    client and the server.
  • Transferring data using a binary format is
    complicated, as problems arise because different
    platforms tend not to represent or order data the
    same way.
  • Therefore XML, a standardised text format,
    becomes an attractive alternative.

7
XML..
  • It is a Markup language for describing structured
    data content is separated from presentation
  • XML documents contain only data
  • Applications decide how to display the data
  • Language for creating markup languages
  • Can create new tags
  • XML documents contain only data, not formatting
    instructions, so applications that process XML
    documents must decide how to display the
    documents data.
  • For example a PDA (personal digital assistant)
    may render an XML document differently than a
    wireless phone or desktop computer would render
    that document.

8
XML..
  • XML is a meta-language
  • With HTML, existing markup is static ltHEADgt and
    ltBODYgt for example, are tightly integrated into
    the HTML standard and cannot be changed or
    extended.
  • XML, on the other hand, allows ou to create your
    own markup tags and configure each to your
    liking for example
  • ltWebEngHeadinggt
  • ltWebEngSummarygt
  • ltWebEngReallyWildFontgt
  • Each of these elements can be defined through
    user defined document type definitions (DTD) and
    stylesheets and applied to one or more XML
    documents.
  • There are no correct tags for an XML document,
    except those defined by the author

9
XML applications
  • XML permits document authors to create markup for
    virtually any type of information.
  • Authors can create entirely new markup languages
    for describing specific types of data, including
    mathematical formulas, chemical molecular
    structures, music, recipes etc.
  • XHTML
  • VoiceXML (for speech)
  • MathML (for mathematics)
  • SMIL (the Synchronous Multimedia Integration
    Language, for multimedia presentations)
  • CML (Chemical Markup Language, for chemistry)
  • XBRL (Extensible Business Reporting Language, for
    financial data exchange)

10
DTD valid wellformed
  • An XML document optionally can reference a
    document that defines that XML documents
    structure. This document is either a Document
    Type Definition (DTD) or a schema.
  • A DTD (document type definition) is a syntactic
    specification used as a model for XML documents.
  • It contains definitions of the elements and their
    attached attributes.
  • When an XML document references a DTD or schema,
    some parsers (called validating parsers) can read
    the DTD/schema and check that the XML document
    follows the structure that the DTD/schema
    defines.
  • If it conforms to the DTD/schema it is valid.
  • If the parser can process an XML document
    successfully it is well-formed (syntactically
    correct).
  • By definition, a valid document is well-formed.

11
XML Parsers
  • Processing an XML document requires a software
    program called an XML parser (or processer).
    These are available at no charge in many
    languages (Java, Python, C etc.).
  •  
  • www.xml.com/xml/pub/Guide/XML_Parsers
  • Parsers check an XML documents syntax and enable
    software programs to process marked-up data. XML
    parsers can support the Document Object Model
    (DOM) or the Simple API for XML (SAX).
  • DOM Build a tree structure containing the XML
    documents data
  • SAX Process the document and generate events

12
Structuring Data
  • Element types
  • Can be declared to describe data structure
  • XML elements
  • Root element
  • Must be exactly one per XML document
  • Contains all other elements in document
  • Lines preceding the root element are called the
    prolog
  • Container element
  • Contains sub-elements (children)
  • Empty element
  • No matching end tag
  • In HTML, IMG
  • Terminate with forward slash (/)

13
Example 1
  • Declaration of XML version

Outside DTD needed webengxml.dtd SYSTEM keyword
lt?xml version"1.0" standalone"no"?gt lt!DOCTYPE
WebEngModules SYSTEM webengxml.dtdgt lt!
comment any text --!gt lt WebEngModules
xmlnsWebEnghttp//www.webeng.ac.uk/gt lt
WebEngTitlegtXML Lecturelt/ WebEngTitlegt lt
WebEngSummarygtAll about XMLlt/ WebEngSummarygt lt
WebEngHoursgt2lt/ WebEng Hours gt lt
/WebEngModulesgt
Root element outermost element in document
denotes start and end points
Descendants of ltWebEngModulesgt element
14
Extensible Style Language (XSL)
  • xmlns
  • Defines an XML namespace
  • Identifies collections of element type
    declarations so that they do not conflict with
    declarations of same name created by other
    programmers
  • Predefined namespaces
  • xml, xsl
  • Programmers can create own namespaces
  • ltTitlegtXML Lecturelt/Titlegt
  • ltTitlegtCGI Lecturelt/Titlegt
  • Can be differentiated by using namespaces
  • ltWebEngTitlegtXML Lecturelt/WebEngTitlegt
  • ltObjectDevTitlegtInheritance Lecturelt/ObjectDevTi
    tlegt

15
Example 2 XML file
lt?xml version "1.0"?gt lt! Web Eng letter
formatted with XML --gt lt!DOCTYPE letter SYSTEM
walter.dtd"gt ltlettergt ltcontact type
"from"gt ltnamegtWalter Enginelt/namegt ltaddress1gt23
Harley St.lt/address1gt ltaddress2gtlt/address2gt ltcit
ygtSunderlandlt/citygt ltpostcodegtWE6
0DDlt/postcodegt ltflag gender "M"/gt lt/contactgt lt
contact type "to"gt ltnamegtT. Blairlt/namegt ltaddr
ess1gt10 Downing St.lt/address1gt ltaddress2gtNice
Arealt/address2gt ltcitygtLondonlt/citygt
ltpostcodegtlt/postcodegt ltflag gender
"M"/gt lt/contactgt ltsalutationgtDear
Sirlt/salutationgt ltparagraphgtWe would be very
happy to teach about Web Engineering.lt/paragraphgt
ltclosinggtAll yourslt/closinggt ltsignaturegtMr.
Enginelt/signaturegt lt/lettergt
16
Document Type Definitions (DTD)
  • Document Type Definition
  • Specify list of element types, attributes and
    their relationships to each other
  • Optional, but recommended for program conformity
  • !Element
  • Element type declaration defines the rules for
    an element
  • Plus sign () one or more occurrences
  • Asterisk () any number of occurrences
  • Question mark (?) either zero or exactly one
    occurrence
  • Omitted operator exactly one occurrence
  • PCDATA
  • The element can store parsed character data

17
Document Type Definitions (DTD)
  • !ATTLIST
  • Defines attributes for an element
  • IMPLIED
  • Can assign its own type attribute or ignore
  • REQUIRED
  • The specified attribute must be declared in the
    document
  • FIXED
  • The Specified attribute must be declared with
    given value

18
Example 3 DTD file
lt!-- walter.dtd --gt lt!ELEMENT letter (contact,
salutation, paragraph, closing, signature
)gt lt!ELEMENT contact (name, address1, address2,
city, postcode, gender)gt lt!ATTLIST contact
type CDATA IMPLIEDgt lt!ELEMENT name
(PCDATA)gt lt!ELEMENT address1 (PCDATA)gt lt!ELEMENT
address2 (PCDATA)gt lt!ELEMENT city
(PCDATA)gt lt!ELEMENT postcode (PCDATA)gt lt!ATTLIST
flag gender (M F) "M"gt
  • walter.dtd
  • Declare elements and elements attributes
  • IMPLIED indicates attribute is
    unspecifiedsystem gives it a value
  • CDATA states that attribute contains a string
  • PCDATA specifies parsed character data
  • EMPTY specifies element does not contain content
    (commonly used for attributes)

19
Example 3 IE display
20
Customized Markup Languages
  • Customized Markup Languages
  • Can create own tags to describe data, creating a
    new markup language
  • MathML
  • Wireless Markup Language (WML)
  • Extensible Business Reporting Language (XBRL)
  • Electronic Business XML (ebXML)
  • Financial Products Markup Language (FpML)

21
MathML
  • MathML
  • Developed by W3C for describing mathematical
    notations and expressions
  • Amaya browser
  • www.w3.org/Amaya/User/BinDist.html

22
WML
  • Wireless Markup Language
  • Allows portions of Web pages to be displayed on
    wireless devices
  • Works with Wireless Application Protocol (WAP)
  • www.wapforum.org
  • www.xml.com/pub/Guide/WML

23
XBRL
  • Extensible Business Reporting Language (XBRL)
  • Facilitates the creation, exchange and validation
    of financial information
  • Namespaces
  • Minimize conflicts between XML elements with the
    same name
  • Example
  • ltschoolsubjectgtEnglishlt/schoolsubjectgt
  • ltmedicalsubjectgtThrombosislt/medicalsubjectgt

24
ebXML
  • Electronic Business XML (ebXML)
  • Used for exchanging business data
  • www.ebxml.org

25
FpML
  • Financial Products Markup Language (FpML)
  • Emerging standard for exchanging financial
    information over the Internet
  • www.fpml.org

26
Other Markup Languages
  • Chemical Markup Language (CML) www.xml-cml.org
  • VoiceXML www.voicexml.org
  • Synchronous Multimedia Integration Language (SMIL
    ) www.w3.org/AudioVideo
  • Vector Markup Language (VML) www.w3.org/TR/NOTE-
    VML
  • Product Data Markup Language (PDML)
    www.pdml.org
  • Commerce XML (cXML) www.cxml.org/home
  • XMI (XML Metadata Interchange) www.omg.org
  • Trading Partner Agreement Markup Language (tpaML)
  • www-4.ibm.com/software/developer/library/tpaml.
    html
  • Small to Medium Business XML (SMBXML)
    www.smbxml.org
  • Financial XML (FinXML) www.finxml.org
  • Financial Information Exchange Markup Language
    (FixML)
  • www.fixprotocol.org

27
Using XML with HTML
  • XML documents are data sources
  • XML documents embedded in HTML documents
  • Using the XML tag
  • Embedded XML document called a data island
  • ltXML ID xmldocgt…lt/XMLgt
  • Marks boundaries of data island
  • Attribute ID
  • Name used to reference the data island
  • DATASRCname attribute
  • In opening TABLE elements start-tag, binds
    specified data island to table
  • To use bound bound data
  • Use SPAN element with a DATAFLD attribute

28
Document Object Model (DOM)
  • Document Object Model (DOM)
  • Retrieving data from a text file impractical
  • DOM created when XML file is parsed
  • Hierarchical tree structure
  • Node Each name in the tree structure
  • Single root node contains all other nodes
  • Tree structure for article.xml

29
Document Object Model (DOM)
30
Extensible Style Language (XSL)
  • XML documents can be placed in their own file
  • Referenced in HTML document
  • ltXML ID name SRC fileName.htmlgtlt/XMLgt
  • xslfor-each element
  • Iterates over items in specified document

31
Microsoft Schema
  • Schema
  • Microsofts expansion of the DTD
  • Called XML-Data
  • Developed to a schema create document definitions
    using XML syntax
  • Schemas or DTDs
  • May be used to specify documents grammar
  • DTDs may be preferred because Microsofts schema
    language is proprietary technology

32
Extensible Hypertext Markup Language (XHTML)
  • XHTML
  • Allows
  • Complex documents to be created by combining HTML
    elements with XMLs extensibility
  • Ability to create new elements
  • Example XHTML document might combine HTML
    elements with MathML and CML elements
  • Well formed documents
  • Each XHTML document validated using DTDs
  • Features provide structure HTML lacks
  • Uses XML syntax
  • All tags lowercase and closed

33
Validation of xhtmlExample.html
34
Microsoft BizTalk
  • Internet data exchange
  • Sending data between organizations is difficult
  • Different platforms, applications and data
    specifications
  • XML simplifies data transfers
  • Microsoft BizTalk
  • Manages and facilitates business transactions
  • Ensures uniformity
  • Three parts
  • BizTalk Server
  • BizTalk Framework
  • BizTalk Schema Library

35
Simple Object Access Protocol (SOAP)
  • Data transfers
  • Clients little processing power, invoke method
    calls on other machines
  • Behind firewalls
  • SOAP messages
  • Envelope structure for describing a method call
  • Request remote procedure call
  • Response HTTP response containing results of
    method call
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